Well apart from it being illegal to go over 300fps there is a question where and how do you play.
For legal terms you cant just crank your marker up and go hey it goes quicker.
You need to go to a site with a chroney and get it under 300fps, Id say at 280fps because if it spikes it will need room to stay in the legal limits.
CO2 is more unreliable than Air so high and low spikes are more likely which as stated above could cause problems.
Even if you are just shooting at home anything over 300fps changes the law to make it a fire arm and not an air gun and you can be arrested,
The "advantages" of turning up are purely functional.
If you want a ball to go further you need more pressure behind it. When I had a problem with my Impy it was running at 230fps the balls would reach the back of the field but by the time they got there they would not break.
If you are playing rec then it will be the same idea the further away the target the less chance of a breaking paint ball
If you dont know what you are doing dont just crank up the marker, take it to a local site and get them to check it all first.