39$? Woah now I regret buying mine for 51!!
Well,personally I would say out of the color tamagotchis it looks to be the best, I haven't recieved mine yet, it's in the way, but I've looked around it a lot and it looks amazing.
Also for me is the best becasuse it's the only version that has my 3 favourite characters (Kikitchi, Ura Mametchi and Meloditchi), and it's the only iD L that has the new designs for Meloditchi and Lovelitchi I think.
Overall it has the cutest characters, and the best thing is that most of them come from older versions, so the nostalgia will make you enjoy it even more~
It also has some cool features the regular one doesn't have, like getting the red outline from the Akai series and visiting vintage locations, and getting heshin jo characters in the 15th iD L is also much easier.
Also the default backgrounds seem to be brighter than the regular iD L's, I can't really tell xD
Though I don't like the games on the 15th anniversary that much, It doesn't really matter since you can download more, so if you have a chance to get one go for it
Also, to me it's better than the P's, but that's mainly cause I dislike most of P's characters (And the ones I like sadly come from pierces), and I don't like the shell either. So yeah, 15th iD L all the way~