Berdych definitely has the least power of the three (but best placement), Del Potro probably has the most top end speed on the forehand but is a lot more conservative than the other 3 and tends to almost push his backhand. Soderling hit the ball the hardest on a consistent basis and also used the most topspin, giving a really heavy ball. He was also the only one who really crushed his backhand as well as his forehand. Soderling also had about 5-10 mph on the other 2 on the serve.
The game lost a great player in Robin Soderling, he could have possibly snuck a major and IMO was just as good (if not better) a player as Del Potro.
Btw, I just checked and Bastad 2011 was his last tournament. He beat Berdych 6-1 6-0 in the SF and Ferrer 6-2 6-2 in the Final. Just an amazing performance, its a damn shame he retired at basically the top of his game.