Well, if you're planning on buying a full suspension bike its best to make sure you pay good whack for it as these bikes tend be more complicated to maintain, cheaper bikes are more likely to go wrong. Also cheaper bikes tend to be heavier which can be a bit of pain when you want to transport the bike or riding uphill. Wet, muddy British mountain biking is especially hostile to full suspension bikes, although proper post-ride cleaning and lubing helps a lot and better bikes have pivots that are more durable, better protected and easier to service. So yeah, if you are buying full suspension and you intend to get alot of use out of the bike and are serious abour your riding be prepared to pay $$$, you wont regret it.
Hardtail bikes are cheaper, easier to maintain and not as heavy due to there being less peices. With no pivots, rear shock and other complications, there’s simply less to wear out or go wrong with a hardtail. That means you spend more time riding and less time on repair and maintenance. Also with hardtail bikes you can get a way better quality and lighter frame for less money, so you will still have a swish looking bike! And, by the way, I have alot more respect for cyclists who use hard tails as they take way more skill to manuevre than full suspension bikes.
Oh yeah, and on hard ground and long distance rides hardtails are better for energy efficiency as less energy is wasted in bouncing the suspension up and down hile u peddle!
Thats my 2 penny contribution, please do your research, and go into some bike shops and test some bikes out, maybe even rent a couple of bikes for a day until you really know what you're looking for.