i'll just say this. having used all 3 for a bit now, i have come away with the following conclusions:
1. there is little place for the stock s20. unless you're hell bent on the small form factor, it's outclassed by the others in every way
2. the ultra is too big. i know the dimensions don't really portray it, but carry it around in your pocket and try to use it every day and you notice just how unweildy it really is. also, over time you start to notice the weight difference and it's annoyingg. finally, i'll come right out and say it...you're buying this specifically for 100x zoom capability. if you want that and can make use of it, go for it. otherwise, ppl (and reviewers) will begin to notice in due time that the s20 plus actually has the better overall camera rear system...
3. s20 plus is where all the attention should be. i understand why it's not (100x ZOOM!! WOW!!!), but it should be. perfect form factor, best screen to size ratio of any phone in history (true statement, look it up), better pixel density, better overall camera system (come back here in 30-60 days), lower price. when the dust settles over the ultra hysteria, this is the conclusion everyone will have. trust me