There will be DG battles on Cataract too, and the winners of those will still gain the advantage. Again, the primary difference is that they happen later on once people have had a chance to gain some levels and items. 

Mixing up your map selection is good so you don't get sick of any given one, which is usually my motivation whenever I do in fact play Prison. The other thing I like about it is that there is no health flag that skews DG engagements for whichever team holds it at the time. This fact is actually making me warm up to the map quite a bit. However, your claim that Prison somehow requires more skill, is silly. DG engagements are DG engagements whether they occur immediately or later on.