he pretty much had it spot on, you don't need an fs bike, they ride better on bumpy trails and for dh but they're by no means required for trail riding. i have a full suspension xc bike and a hardtail singlespeed, hardtails are more efficient but you get bounced around a lot more on them, especially aluminum hardtails. if your back get jostled easily or something then go with either an fs bike or ride titanium or steel to get more give
i personally like the bounce of aluminum to hop around corners but some people hate it
i much prefer full suspension but it's your call, start out with a hardtail because they're cheaper and then take it from there