technically you do get a bit more surface area...
for example on contact coils your wick is just touching lets say 60% of the inner circumference of the wire as the next wire prevents the wick to "hug" a bit more circumference of the coils, with spaced ones your wick is free to hug a bit more of each individual loop thus giving you more surface area
Considering its not flat wire, when the wick expands it would have the same effect on non spaced. If there was a difference, it would be negligible. I still say the main difference is more wick material inside the heating area, not coil surface area. The only real way to increase surface area of round wire is to do build like twisted wire, Clapton's etc..