So when I say easy and hard I mean a whole lot of things, including but not limited to the following. Since I don't expect people to describe all their plants, how about the extremes:

Easiest or hardest to grow from seeds.

Easiest to root or hardest to root.

Easiest to bloom or hardest to bloom.

Floriferous or Stingy with flowers.

Fastest growing and slowest growing.

Bug free vs. bugs are a constant battle.

Easiest overall to grow and trickiest to grow.

I could go on and on, but I'll leave it at that for now--feel free to add your own categories of course. List your favorites for one category, several or all. Some of these will of course depend on your conditions--in a pot or in the ground, climate, etc.

My experience:

Seeds: I've only grown P. edulis, and not to blooming size. It was neither easy nor hard.

Rooting Cuttings: Easiest--P. colinvauxii (roots in 5 days, probably less). Also easy P. sanguinolenta, P. parritae x antioquiensis. Hardest so far: P. membranacea (nothing yet). Hard but not impossible--P. tripartita var. mollissima.

Easiest to bloom: P. 'Blue Horizon', P. 'Lavender Lady', P. exoniensis (antioquiensis x tripartita var. mollissima). Hardest to bloom (decent sized plants and no sign of buds yet): P. tripartita var. mollissima and P. membranacea (these may both be seasonal due to summer temps. Both have probably just reached blooming size).

Most floriferous: P.'Blue Horizon', P. 'Lavender Lady', P. exoniensis, P. edulis. Mine either bloom a lot or not at all.

Fastest growing: P. membranacea (!), all Tacsonias and P. edulis. Slowest: P. sanguinolenta (this is likely my fault).

Worst bug problems--spider mites love all Tacsonias. P. edulis and P. membranacea have been relatively bug free.

Easiest overall--P. 'Blue Horizon', P.'Lavender Lady' P. exoniensis and P. edulis. Tacsonias grow well here (but may be more difficult to bloom except for P. exoniensis); they are difficult in most of the country.

Easiest to grow from seed: Anything I fruited myself.
Hardest to grow from seed: Anything I purchase.

Easiest to root: I would agree that P. colinvauxii is among the fastest, though we have rooted P. 'Witchcraft' and P. citrina, (just those two off the top of my head, though I am sure there are more), in just as little time.
Hardest to root: Again, I would agree that P. membranacea is a rooting nightmare. Others that are supposed to be very hard, like P. herbertiana and P. aurantia, we can do so much easier than this one. Though, I would say if we throw the season into play, any Tacsonia would be the hardest for us to root in summer, since we do it outdoors. in fall/winter, they throw roots with no problem.

Easiest to bloom: If they bloom without trying, does that count? If so, I can't do this one. There's too many to name.
Hardest to bloom: 1/4 of my collection that haven't bloomed yet. Not going to list them all...
...And, I don't consider it blooming if I bought it with flowers or buds. It has to bloom the second year I own it for it to count. The one exception would be if I got it as a very small plant or cuttings only, and got it to bloom the first year.

Most floriferous: Most flowers, or longest flowering period? P. 'Incense' wins for most flowers, hands down. 80-120 flowers per day from June to October. Longest flowering period, (outside only), would be P. x violacea. April to January, approximately.

Fastest growing: another that I cannot answer... too many growing fast right now.
Slowest growing: P. nephrodes, though that is likely my fault, just like your P. sanguinolenta is. Also, any Tacsonia, we just get too darn hot here.

Bug issues: P. 'Witchcraft' without a doubt. I cannot keep spider mites and scale off this plant. Every year he gets attacked harshly. Thankfully, he is large and well established, so he can withstand it.
Least bug issues: most anything Passiflora/Stipulata, except perhaps P. actinia,(he gets mites).

Easiest overall: It's a big fat tie between P. 'Incense', P. 'Amethyst', P. x violacea, P. caerulea, and P. 'Indigo Dreams'. All of these have been in the ground for 8+ years and grow and bloom every year without any, (I mean... ANY), effort whatsoever.
Hardest overall: Any of Tacsonia supersection.

All of this is of course based on my experience alone. Everyone's location, growing skill, and a multitude of other aspects need to be taken into account. The fact that "mark4321" and I live only 2 hours drive from one another, though we have had massively different experiences, illustrates this perfectly. Where he has P. x exoniensis thrive tremendously, and I have P. sanguinolenta bloom for most of the year, though neither of us has the opposite successes, is a great example.

Good luck with your Passiflora growing. Whether someone says it is hard or easy, my advice to all would be to attempt whatever you want to attempt. Learning for yourself what works and what doesn't is half the fun of growing plants. Experiment... try new things... grow something that no one seems to want, but you find beautiful... enjoy the art and zen that is gardening. Then, live or die, bloom or wilt, you will still appreciate the time and the efforts you put into them.

I'll climb off my soapbox now...

Happy gardening!
Eric

Yeah the question is probably a bit overwhelming, but "easy" means so many things to different people. Some people couldn't care less if it's easy from seed; others consider that one of the most important considerations. For others temperature tolerance (not on my list--less important to me) is the number one consideration. Say what you want to say.

I suppose one way around all this is just to mention which you consider "easiest" overall and explain why. Or don't explain why if it's too much hassle--it's still incredibly useful information to just have a list.

Eric, a specific question. I had no idea that Incense bloomed like that--that's amazing! How big is the plant? Do you have any idea whether the "improved" Incense (related) crosses--such things as 'Blue Eyed Susan', 'Temptation' and 'Elizabeth' are equally floriferous?

In case anyone is curious why I say P. saguinolenta is "my fault". The plant was growing really well until I repotted it in a clay pot and forgot to water it a couple times. Actally, come to think of it, 'Elizabeth' may well be slower. However severe snail attacks slowed it down considerably.

So all sorts of factors will no doubt affect our observations. But still, something like P. colinvauxii's rootability or P. 'Incense's floriferous should be true for many people. And I think most people do find P. memberanaecea difficult to root.

Which passionflowers do you consider the easiest and hardest? Include one or more factors such as propagation, ease of blooming and floriferousness, speed of growth, problems with pests, temperature tolerance, and most importantly which passionflowers rank high or low overall. And of course include your own criteria--whatever is important to you.

It's still not a simple question, but at least it's one question.

Okay, our Passiflora 'Incense' is grown on a chain link fence which is 6 feet high. The vine is fairly evenly split each direction, about 25 feet in total. It also pushes stems "out" all over the place, which creates depth of about 2 feet on each side. The bottom 2 feet is fairly bare, so I don't count that. Still, not counting suckers, that accounts for about 400 cubic feet of clustered, dense vine.

Our P. 'Blue Eyed Susan', 'Temptation', and 'Inspiration', (which is what I think you meant to type instead of 'Elizabeth', which is not the same hybrid), are all fairly young, so it is hard for me to make a determination as to how they will be. I have heard some people say that they can be just as rampant, and others that they have larger flowers, but not as many. Even more confusing, I have read that they do not sucker like P. 'Incense', but have a person with first hand experience who has had them sucker. One fear that I have is that I do not know how reliable the sources for these plants are. I trust the people who gave them to me, but I have no idea of their source. I guess I'll find out, and let you know. So far, they are growing pretty fast. It's still tough to compare being that our P. 'Incense' is 8 or so years old, and has a stem like a small tree.

Hope that helps a bit.
Eric