Earlier quoted context omitted.
Are you sure about the rear suspension? Yes, it can save your wheel in some situations (which you should really be avoiding as an amateur), but %99 of the time it's unnecessery weight that also happens to eat some of the power that'd normally go to the wheel. (I'm not a competitive biker, mountain or otherwise, I'm just curious)
I would say that if you're riding on rough terrain (e.g. rocky, boulder-strewn, heavily rutted, etc.), you would be shocked at what you can do on a full suspension bike. I know I spent the first couple of months with a F/S bike just riding over random obstacles out of sheer amazement. If you're riding mostly smooth dirt trails where your primary obstacle is occasional tree roots and ruts, then a hardtail is probably…
http://www.bikemag.com/news/guy-wins-megavalanche-division-o...
(Admittedly, full suspension is probably a bit more forgiving than a hardtail, but I have more fun on a hardtail).