>>Some have the crankset behind the front wheel>>
As mentioned, such 'bents are referred to as having a long wheelbase (LWB). These bikes are well suited for riding long distances out on the open road. The longer wheelbase provides a smooth, relaxed ride. Most LWB's can be excellent touring machines. Some models can go quite fast as well. On the downside, the long wheelbase can make storage and transport somewhat of an issue. They can be a bit awkward to handle and have a large (wide?) turning radius.
On the other side, short wheelbase recumbents (SWB) have the cranks extending out beyond the front wheel. SWB's can offer quicker, more responsive handling...not quite so sedate. They have a shorter turning radius and are easier to store and transport. SWB's also tend to weigh a bit less and might prove to be a bit better on climbs. The ride can be a little harsher, though, as the shorter wheelbase won't soak up the bumps as well.