I have too many favourite versions so this will take a while lol
Let's start with colour ones~~
15th anniversary iD L
1. One of the most important things to me on every tamagotchi is the set of characters, and the set of characters of this version is THE BEST, not only it has my 3 favourite characters (Kikitchi, Ura Mametchi and Meloditchi) but it has a huge variety of cute characters I've loved from other versions, including characters from every generation. Plus, the exclusive characters to this version are absolutely adorable, who wouldn't love Momotchi, Otogitchi or Rednosetchi (not exclusive but only raisable in this one) <3
2. The destinations, Makaka town, the space one, UraTama Town, they are all really unique and really fun, making raising all the characters to tamatomo definetly worth it!
3. Is an iD L, I believe the iD L is the best colour version, all the features such as seeds AND ALL THE DOWNLOADABLE CONTENT make it superfunnnn <3
4. The purple shell's silver part looks really cool, is a weird mix of silver/gold depending on the light xD
Tamagotchi + color
1. The screen, the screen of the +C is a lot better than other colors, it's bigger, and the colors look a lot more alive, it gives a really nice kind of pastel relaxing feeling xD
2. The shell, I believe this tamagotchi has the best shell ever, simple, easy to hold, easy to place anywhere, and with a huge variety of colours to choose from
3. The Animations, the animations and sprites on this version are the best, not only the characters sprites and close ups, but also the weather and extra animations, the seasonal animations are perfect
4. Fun destinations and games, specially the games, even if they are just 3, they never get boring~
The iD is also really cool, it feels really personal and it's a lot of fun with the loads downloadable content you can get, it will never get boring because you can keep getting new things all the time
And the P's is great because you can get the iD and iD L's stuff and because english lol
Okay connections/plus now~
Uratama
1. Character set again, I love the Ura Characters I think they are all supercool and I want to raise so many of them, they have something special
2. The screen, the blue pixels are amazing, specially if you are into photography, the colour of the pixels changes depending on the light, so the screen could have a really shiny blue look, or it could be rather dark blue or even black, it's really fun to see the different shades of blue you can get by changing the lights
3. The growth process, it's not as fast as the newer versions, so you have more time to enjoy the Tamagotchi's worth, and the nanny and teachers are all really cool too~
V5 / Familitchi
1. Animations, the animations of this version are probably the cutest out of the connections, specially when you get a Pure Family, they are so cute you won't want to marry them xD
2. The games, BEST GAMES EVER, the tea time one and the golf put are so challenging and fun, and the TV one and shoes one are not boring either, all of them are fun <3
3. THREE characters at a time, and PARENTS! you can raise more than a character at a time, I love seeing them dancing around the screen
4. Expensive items, it won't be too easy to get all the items, this is a great thing xD
V6 / Music Star
1. Quality, the quality of this tamagotchi is amazing, it doesn't get scratched as easilly as the other versions, both shell and screen, is the only Tamagotchi I have from my childhood that looks like brand new after all this years.
2. Music Based, I love music and this tamagotchi is really fun to me, getting all the trophies is really fun
3. Spot/Mocha costumes, Spotchi and Mochatchi are too adorable, they make me like this version a lot, and when I get a character I don't like, I can just make it wear the costume lol
4. The shells, the music star have really amazing shells, the V4.5 and V6 probably have the best shells in connections xD
V7 / Tama-Go
1. The shell design, it makes the Tama-Go look like one of those decorative eggs you find in fancy houses, only that with little characters jumping inside it
and FACEPLATES, the faceplates are so cool, you can make your tamagotchi look however you want, it's perfect <3
2. Greyscale rooms, I love changing rooms on colour tamagotchis, and I love it even more when I get to do it in a B/W for once lol
3. Food shop, since there are no items you can buy more food, this way you can make sure to give your tamagotchi a huge variety of meals xD
4. LOTS OF GAMES within the figures, 5 built in + all the figures ones, this version won't get boring no matter how you look at it
5. Really good set of characters, Necktietchi, Lovelitchi, Uwasatchi and Grippatchi are all exclusive to this version when it comes to english releases, it also has my fav set of babies ever and all the adorable iD teens, and adult Kikitchi <3
I also really like the V2, it's really simple but cute somehow, and it has lots of vintages charracters that haven't appeared since.
Now Vintages~~
Genjintch
1. really good set of characters, not many people care about the genjintch characters, but I think they are really interesting and some of the really cute (Monkeetchi <3)
2. two-way-evolution, I believe this is the only version that has it, making it really unique
3. Cool sounds and shell, it's hard to find cool brown-looking Tamagotfchis lol
Devilgotchi
1. Oposite to the angel, all the things I don't like on the angel I like them on the devil, evil characters that try to trick you, doesn't it sound superfun?
2. Growth depends on evil power, rather than care, making it interesting and challenging to raise the evil powers of your lil demon
3. Really cool secret animations and characters
4. Slow growth
P2
1. it has all the good things about the first versions (simpleness), but with better characters xD
The Morino and the Osutchi also look really cool, they have really adorable characters
Those are pretty much all my favourite versions and why I like them~