There's an old saying... (paraphrased) "The best time to plant a tree is 10 years ago... the next best time to plant a tree is today"

I asked the same questions you did a few years ago, and I think I can answer part of it for you even though I'm in zone 10.

Drawbacks are, expense and if there's a problem and the tree dies it's harder on you.

The plus(es) have been for me less wait, sometimes. Also seeing a larger tree instead of a twig in your landscape is cool.

On the down side, size doesn't ALWAYS guarantee production sooner.

I've purchased carambola, and canistel with fruit on it, put them in the ground and waited years for them to fruit.

Slow growers are good candidates if you want fruit sooner just because age and size help produce... then there are trees like Jackfruit that need a sturdy trunk to carry heavy fruit that getting larger is a good idea.

It's aggravating having a larger tree that is barren when some others of the same cultivar are a stick in a pot giving up fruit :-)

So, regardless of your zone I think there are some constants and risk.

to me,
it has a lot to do with how fast the tree grows.
i can not understand why someone would want to pay $50 on a papaya tree thats less than a year old
when they grow from seed to fruit in 1 year anyway.

If you have the $, then by all means go ahead

but , for a fast growing tree, i cant justify the cost
for my budget ,, anyway.