I don't know if the Shengshou 5x5 is more popular than the V-Cube. Also, under 6x6 when you say the V6 takes some modding, you're being extremely modest. It's the most labor intensive mod the average speedcuber will undergo. Even if you choose to do the mod there's no guarantee that it will be successful. The V6 is good if you're:
a) Fast at 6x6 and can mod well
b) Slow enough that you don't care and may want to mod in in the future
c) You want it to complete your V-Cube collection
The Shengshou is WAY better out of the box. If you're competitive in 6x6 and enjoy it but don't have the time or ability to mod it, then the SS is the way to go BY FAR