Purest form?! I didn't know that chess had a pure form. I figure you mean in how two people sit down to play a game, but if there is to be a pure form then it would have to be social, and live. Thus, meeting someone at a local club, or cafe for a game while socializing would be closer to a "purest form" of playing the game. Especially when you consider that millions of people play the game at least once week, and they don't all play in tournaments or for points.
That said I believe all on line variants are a plus. Live chess has proven to always fall into blitz chess with 5 0 and 3 0 being the norm. This can't be purest at all. Turn chess as it is now being called here at chess.com allows people like myself who must work for a living, yet find a way to get on line during the day..shh 
, to play when possible. This variation is great as it forces the game to slow down a bit, and allows one to take their time. It also affords people like myself the ability to jump off line in the middle of a game i.e. "Craig I need this report by noon" and get back on at a later time to continue.
hi, i can`t wait to play live chess on here ,to me it`s the purest form of chess.
i feel if you`ve got time to analyse positions and cross reference positions there`s an amount of playing chess by rote so to speak,and it becomes a compilation of classic lines from a well trodden path. i can understand that some peoples ego`s would`nt allow themselves to do it.(mine anyway!) so to conclude i think turn based chess is more of a method of training than a good scrap across the chequred board.....