If you want a really fast shooting gun, then take the Vs2. But if u like A little less noise and a little slower shooting gun, then take the Ion. If you get the Vs2, then the only thing you need to upgrade is the ASA, because the original one sucks. And if you get the Ion, then upgrade the board if you buy a new one.
I got the Vs2 and its nice but the Ion is great too.VS2 is much easier to lube and maintain. Up to you tho, do your homework......or just read weevers threads =P