Yes, interesting topic indeed.
I've only ever got to play with the V1, V3, and Tama-Go versions. I do remember the vintage Tamas from when I was a kid, but I never personally owned one. I love my V3, it's small and cute, but gets a little repetitive. Although the Tama-Go is a little hunky, it's really not that big and still fits in my jacket pocket, and I love getting my artistic friends to draw me cool faceplates. I also like that you can potty-train your Tama, becase let's face it, we all get tired of cleaning poo after a while. Something that bugs me is that the character evolution growth is based off good/bad care, I like all the characters equally and would prefer if it were random.
The iD L seems to be popular but is a little to flashy in appearance for me, something that keeps my stuck to my Tamas is the nostalgia of the simple shell designs and the black and white pixelated screen.
At the moment, I'd say Tama-Go, but I might change my mind later.