Do you plan to play tournaments? If yes.. you cannot use the VS3. The trigger frame is 1 pull to 2 balls.. Most Tourneys do not allow this.
I Like My Ion.. you've seen the heated battle over how smart parts is a bunch of ass holes and are trying to shut everybody down. I'd either buy a used ion (since the older one's seem to work better) or pick up the new EOS...
Keep in mind though.. Ion = $169 (I think the old style is now) You'll need the following:
68 ci / 4500psi tank ~ $150
Halo B ~ $100 (EGGS SUCK!)
Clamping Feed Neck ~ $30.00 (Stock one is Junk IMO)
If you pick up a used one most of this can come standard.. buy a package for example.
The VS3 runs on a $30 C02 tank.. but still might want the Halo B because it can shoot fairly fast..
Put your comparing a spool gun (ION) to something that works using a Spring.. SHoot totally different, the Ion has no kick.
Example of mods:
Ape Ion For Sale
But do you need all this no, but damn it looks nice and shoots FAST ASS ROPES LIKE NO TOMORROW!
My 2 Cents