I've seen Angels that aren't as expensive as you would imagine (as in, NIB Tamagotchi Angels selling for around $20 or so). You just have to be patient and keep looking on Ebay. Whenever I buy on Ebay, I typically don't jump at the first opportunity to buy a certain Tamagotchi. Sure, I may have to wait a few years to get the one I want (and I have, in some cases) but I end up saving a lot of money by doing so. On the flip side, Uminos can get really expensive. I think the "cheapest" ones these days are around $60 for a NIP one.
Anyway, I guess what I'm trying to say is that you should take money into consideration to an extent when you're trying to decide which ones to buy because you never know about the prices out there. In general, if I were to rank them in order of increasing price, and if they're all NIB, I'd go Japanese Angelgotchi, Umino, Tamagotchi Angel. There are exceptions, however, which goes back to what I've been saying about being patient with Ebay. I'd figure out how much I have to spend (and how much I'm willing to spend) and go from there.
Both of them are really fun. Both have the motion sensor function. One of the biggest differences that come to mind right now is that while the Angels are really low-maintenance (it won't take much at all to get the perfect care characters), many people (including myself) really struggle to get past the toddler stage on the Umino. So, if you don't have free time, you're going to school, or get caught up in the hustle and bustle of daily life, you won't be able to care for an Umino without pausing it all the time. The Umino is one of the most difficult Tamagotchis to care for. That's not to say that it's not fun but if you don't have the time for it, it'll die on you.
Have you researched information on the both of them? It'd probably help you make an informed decision better than we can. There's a website that's been around for ages that has a lot of good information on the vintage Tamagotchis.
HERE is the page on the website for Angels and
HERE is the page for Uminos.
Good luck and let me know if you have any specific questions.
