the
ID is the first color version to introduce downloads, it has fewer overall content and characters compared to all the other versions, however its animations are a lot better than any of the releases that came after it, making it feel more personal, specially if you like the characters in it.
It is also the Tamagotchi with the most downloadable content, aside from the P's conversions, so it's really fun and doesn't get boring easily with all the expansions. (All of them free)
the
iD L is basically an improved version of the iD, it fixes all the iD drawbacks, however,it introduced a new animation system so characters could wear clothes, making the characters have less sprites and making the animations less fluid.
But apart from that is has a lot of content, most of it which is built in, and still keeps being simple, definitely the best version for a beginner
The iD L also has 2 special versions that are a bit more expensive but definetly worth it, those being the 15th anniversary version and the Princess Spacy one (Warning, really girly!)
the
P's is the version that came after the iD L, being the version with most features yet in any Tamagotchi, the P's allows you to take your character to School, Daycare Painting, Jobs, find people on the garden, date in the park, personality skills and user profile.
Other than that, the P's can also have downloads, and since all downloads from previous versions have been converted for the P's, this version has the most overall downloadable content.
The P's also introduced pierces, that are little expansion packs that will let you get even more characters, transformations, items, games and destinations.
It also has faceplates like the Tama-Go, but sadly the jewel-like pattern can't be removed xD
the
4U has the fewest built in characters out of all of them, having only 10 adults and skipping completely the teen stages, it also has less features than the P's so is around the same as the iD L. It also has some new features such as training skills and nanny care, as well as having clearer faceplates. It can have a lot more content with downloads, but you need a Nexus 7 (as its the cheapest) tablet to get them, making it really expensive.
I don't recomend this version for beginners at all xD
If you are planning on getting one of those I think the iD L is your best bet, it is simple and has a lot of content and the characters are most of them adorable. If you really enjoy your iD L then you can go for the more complex P's after, the iD L gameplay lasts about 5 motnhs, so you have time enough to enjoy it
The iD L has an official english version too, if you don't mind paying 3 times more for it, the P's has a english patch that's free, so those 2 are also the ones you can enjoy in english too.