Well, for a hardtail, a jump/freeride trail bike will be as close as you can get to a downhill bike.
'Real' DH bikes will, of course, be full suspension, and those might differ a little from a 'real' full suspension freeride bike.
Strict dirt jumping bikes will probably have a rigid fork, small, short frame, and single speed with only one brake in the back. The kona stuff/cowan are a good compromise... they have gears, suspension, and good geometry for trail riding OR jumps. Not as good for trails as a Stumpy... possibly not as good for jumps as a dirt BMX.