The stock V-brakes on my bike have actually thrown me over the front. When braking from a decent speed, it gives a lovely "wobble" on the front wheel. Absolutely terrifying when you need to stop quickly I was going to go for disks, but anything in the price range I was looking for were just bits of tinfoil.

Personally, I think that disks are overrated. Cheap disks are just tinfoil, and expensive ones add a considerable weight (Note I've never actually weighed an expensive bike disc, but I'd imagine they'd be fairly similar to 50cc quad disks, which I have weighed [And FWIW are also tinfoil when used on quads. I've seen warped ones after 2 hours use]). Hydraulic ones even more so. Mighn't make a difference if you're doing downhill, but I prefer to have the bike as light as possible when going uphill

For road use anyway, disks are a waste

Discs add hardly any weight, I've weighed. And V-brakes don't clog up unless you are going through knee-deep mud, but they only make noise as they usually rub the mud off.

Suspension adds a bit off weight, but it's the spongeyness that takes away all your speed. Try tighten it up to a suitable weight, or lock it fully. Rear suspension is pointless too, unless you are doing big air jumps.

But I don't know much about Mountain Bikes, I do velodrome, road race and time trials sometimes.

Quote from piggy501 :

Discs add hardly any weight, I've weighed. And V-brakes don't clog up unless you are going through knee-deep mud, but they only make noise as they usually rub the mud off.

Suspension adds a bit off weight, but it's the spongeyness that takes away all your speed. Try tighten it up to a suitable weight, or lock it fully. Rear suspension is pointless too, unless you are doing big air jumps.

But I don't know much about Mountain Bikes, I do velodrome, road race and time trials sometimes.

I've a friend with a nice gash on his face because there was water on his rims. He hit his brakes hard enough to stop himself, then the water wore off and he endoed. I've also got a nice scar on my leg from a log thanks to a massive build up of mud and snow/ice (no stopping power followed by crash, then I realized that my brakes wouldn't release due to build up of muck on the cable). But honestly, I'd go with V brakes on a bike in the OP's price range. They will just do better. Also what was said about rear susp. is true and false. On flat ground some designs/shocks cause a lot of bob (like you said), but there are some designs/shocks that eliminate this (Spesh Brain shock comes to mind). Also, for things like rock gardens and roots FS bikes are nice. They also handle better (in most situations). And yes FS rigs are nice big air.