The 230 HP dakota loses 7 knots without the wheel pants. Max cruise is 143 per book.
It is simply that retractable gear is not cowled so it drags when hanging out
I think it’s more than that – I think many retract gear systems are extra draggy due to all the other bits that fixed gears don’t have, such as gear doors, the various extra struts to make the gear go up and down, and the big hole in the wing that’s left when the wheels are down (the Bonanza with inner gear doors is draggier when the gear is in transit and all the gear doors are open than when the gear has finished extending and the inner gear doors are once again covering the big hole where the wheel was).
Incidentally that’s how you tell if a Bonanza/Baron pilot is telling the truth when you go out to their aircraft sitting on its belly on the runway and they say the gear collapsed. If the gear really did collapse, the landing gear is crumpling the inner gear doors up into the wheel wells. If the gear is still behind the inner gear doors, well, the truth is that for whatever reason the gear was still retracted on touchdown…
Ahhh, my RG flies 2 MPH slower with the gear retracted, so I leave it extended much of the time….
I think the Dakota is the only PA28 that I would buy if I had to buy one 
By pure chance I have been flying two almost identical C172S models during the last 10 days. One has the wheel pants, the other not. Although these flights were rather short hops in the L.A. basin, so no real cruise performance comparison, the one with the pants does about 7-10kts more than the other. Quite a difference, given the top speed of these things!
