Bob is right of course...to a point. Drag increases as the square of the velocity so twice as fast means four times the drag. That means that even a very small increase in speed requires a lot more power which burns a lot more air.
Or to look at it from another perspective, if you switch from a wet suit to a dry suit, you are going to go a lot slower on the same power even with all the other crap you are dragging through the water. So dry suit drag is a very important consideration if you actually plan on going anywhere during your dives especially given the low overall swiming speeds in scuba diving.
The vulcanized rubber, crushed neoprene, or neoprene suit has a potential avantage as it will have some stretch (a lot of stretch in the case of a neoprene suit) to it which means you can tolerate a snugger fit. A back zip suit is also potentially more streamlined as the extra torso lenght (and bagginess) normally found in a self entry suit is not required.
In this regard, the ideal drysuit from a streamlining perspective is a back entry neoprene suit as neoprene is very stretchy and the suit can be very form fitting without restricting your range of motion. Trilams and other suit materials that do not stretch at all or as much need to be cut bigger to ensure adequate range of motion and are inherently baggier and draggier.
.
