Not familiar with the other two, but your Pom is deciduous, so it won't mind the lack of winter sun.

tropical plants need lots of sun to thrive. They might survive in those spots for years but will definitely not reach their full potential, and probably will not bear fruit as well.

Lychees will need protection from the sun during the summer months especially when it's young. Afternoon shade will be good for it but will still need some morning sun at least.

I'll actually be moderately surprised, and rather pleased, if either of them get big enough to bear fruit.

Sounds like the pom's not in the running, it will likely be happier in the back yard where it will get sun whenever it actually wants it.

Which, generally, would be preferable for either remaining tree, a pot in the back yard with sun all summer and none at all in the winter, or a rather larger patch of dirt with some sun all year?... it's sort of sounding like the lychee might be happier in the front, what with the lower wind and the summer shade.

Most fruit trees need a certain amount of sunlight to produce a good amount of fruit, so they may look healthy but not produce much fruit. If you are just looking for some pretty desert plants for part sunny, you could try golden columbines or aloes or agave

It's more a matter of... I have these seedlings, and I want to put them somewhere, and I'm wondering if either will do better there than they will in the back yard. I suspect a tree will do better than a low-lying plant will, since there's more sun higher up. I'll be posting a picture at some point soon.

Actually the point being made was the pom WOULD be the best for the spot you described because it doesn't care about sun in the winter since it is dormant. Plus it fruits late so the sun in the late spring - summer would work well.

Here's the front area, the grass is in the spot where I'm thinking of putting one of the trees. There's no roof directly above the spot, but there is a roof just to the west, just to the north (you can see the edge of that), and at the top of the wall that's just south of the plot of dirt. You can see the roof a bit to the east, it's maybe 3 yards away.

Hmmmm, maybe a rubber plant would do well there. It looks a bit small and enclosed for a tree to me.

Basically, the question is, will either tree (the mango or the lychee) do better there than they will in a large pot in the back yard, with absolutely no sun in the winter. Those are the possible fates, for those 2 seedlings.