The answer to this is exactly the same as with Tsonga and Berdych. Soderling is the better player and it's not even close. Unlike Ferrer, Robin has the game and the weapons to be a legitimate threat and beat the top 3 in Grand Slams. Achievement-wise, the gap is equally big: Soderling has been to a Slam final (twice) and won a Masters title, both of which Ferrer has never done and never will.
To put it simply, Soderling is in the same league as Tsonga and Berdych (legitimate top 8 players, who can and have beaten all the top players in Slams and have an outside shot at a Slam title with the right combination of form and draw) - which is several leagues above Ferrer.
Anyone voting for Ferrer is either trolling or a frankly delusional Ferrertard/Soderling hater.
Great thread btw