When it comes to DVD's, slower burning can actually be worse. The dye is very sensitive in a DVD--burning too slow can cause irregualar burns just as easily as burning to fast. If you are the patient type, a good rule of thumb is to pick the middle speed of the disc for your normal process--much like Snoop's example. For the 4X's, 2X should work just fine for everything.
Some brands don't do so well at 4X once you pass the 3.5GB point, so that is something to keep in mind if you are having trouble with 4X burns--dropping to 2X should fix the problem. Only burn 1X on a 4X or higher media as a last resort though. It will burn "OK", and it will load--but you may find it loads slowly on the PS2.
In my v5, 2x burns typically load as fast or faster than the original on all media I've tried that would take a 2X burn (even a handful of crappy Princo's). 4X's on my off-brands do OK on straight data loads, but I've noticed some skipping on a few video clips. I wouldn't trust 4X on generics with something that streams content on the fly (GTA, etc)--for that I would definately stick to a 2X burn unless using a trusted higher end Ritek, Verbatim, etc or a certified 8x disc.
If it ain't broke don't try to fix it! But, hell if you can tweak that bastard just a little bit more....hehehe.