What makes you think a young player will definitely adapt to the English game? Kleberson and Djemba Djemba were pretty young when they came to United and they turned out to be the two worst signings in this decade. So its not a guarantee that a younger player will work better.
VDV seems to have adjusted fine. He along with Bale are Spurs' best players this season. So why do you think Sneijder is going to have a problem? Just because Veron did not work, does not mean everyone else who is 26-27 when they arrive will not be good for us.
Real Madrid usually do these kinds of signings. And despite spending tons of money, they are really not that successful. The likes of Zidane and Beckham only contributed to a league gold once each, despite spending five and four years in the Galacticos. Ferguson has not done this kind of signings - the reason for that is; it is not the way to go. Being a great playmaker in Spain and Italy is one thing, in the Premier League there are more tempo and less room, and the difference between 1st and 10th at the table are far bigger in Italy and Spain than in England.
Players over 25 should be signed domesticly, and Ferguson has always preferred the local option when available... Right now it seems that he might have to go abroad and Sneijder is not the solution, because spending £40m on a player and see him flop is very unhealthy for any football club... If Ferguson wanted Snejder he would have signed him one and a half years ago for only €15m.
Sign players on the way to their peak, not someone that clearly is over it. That is not the way to go, and it is really scary to sign a player. I really wanted Sneijder a couple of years ago, but my opinion is that its to late to sign him now. We need a man for the future. Who knows? Maybe Giggs and Scholes is takes two more seasons? Hleb said in a article regarding Michael Ballack that he would never go to England at his age because of the tempo differences, if we sign Sneijder we need him to make a instant impact, and I am not sure if he can do that. Malouda came when he was 27, he needed two years to adapt to the differences of the pace in the game.
That is the problem with comparing van der Vaart and Sneijder is that van der Vaart was a £8m signing with basically no pressure to deliver. Sneijder can easily be five times as expensive... A player flopping at such a price will be very destructive for the team.
Pastore would probably be a better signing than Sneijder. And, I would also like to say, that despite seeing him being linked to ridiculous fees like €40m, I really don't think he will be as expensive. I bet we could get Pastore for €20m in the summer. Pastore would be a lot cheaper than Sneijder, and not to mention far lesser wages.