Sneijder is the better player IMO, with his passing & freekicks especially... A more consistant performer but his little nighling injuries are a concern...
Nasri is a little inferior but is quicker and better at getting round players, scores a few as well... No injury concerns really but can be a tiny bit inconsistent at times...
Mata is probably the fastest and similar to Nasri, decent goals record from midfeild also, but apart from pace, I'd say Nasri has *slightly* all round better abilities, again all IMO.
Pastore is a passer, has a great brain. He knows where he has to be and is tall, so should suit the prem.
Lavezzi is definitely the quickest... But he's also the one I know least about TBH, he's very tricky. He's 26 and IMO not totally 'World Class' like Sneijer at 26/27.
Nasri, Mata and Pastore are the youngest, and Sneijder the best over all, so my list of preference would be:
1) Nasri/Sneijder/Mata (there's no separating them IMO, even though they're slightly different styles of players)
2) Pastore (just, just behind those in 1)
3) Lavezzi (probably change my mind if I saw a bit more of him TBH)