Im in the same boat as you; already picked Nesta which im quite happy with too.
Was going for Keane as "1st pick" but the last few days roberto carlos is getting in my head haha. I use telles now who i also really like but i made a squad on futbin with all the players in the game that i would choose if coins was no issue. Keane didnt make it due to the likes of Vieira and Gullit (how realistic it is to get their non baby version is a different question) but Roberto Carlos did make it since he seems to be the best LB in the game right now. Only point holding me back is that if i dont take keane id probably rather have taken Rio in hindsight which is impossible now since i already got Nesta; and that Carlos is his baby version versus keanes prime. The middle version looks like quite a upgrade to baby carlos. It has little bit less dribbling but way better fysical and passing; and in the dribbling stats the middle one has quite better reactions plus composure.

And i do think Keane is not comparable to gullit or vieira but dont think he is quite far from them. By that i mean that if you look to the players just below gullit and vieira he is one of the best after them. Especially if you use him as CDM only.

but yeah im probably not the best guy to ask since it seems like im getting more and more confused each day