Classic is ok, but the designs are kinda same-ish. Other than the headbands you can't really tell them apart.
I preferred the 2003 version (which followed the comics more and had a better story, nostalgia aside)
Plus each turtle had it's own colour scheme.
2012 version would work too, but the only things that would be different to me would be Mikey's freckles, Don's tooth gap and Raph's beat up shell. And I suppose it would be overall a bit more boxy looking.
Maybe they'll do like Turtle's forever and have all the different version, even the black and white classic comic versions.