My guess is this is as efficient or better than the MoreBeer copper unit.
Copper is slightly more efficient at transferring heat, but the stainless unit has 1/2" inner tubing, where as the copper unit has 5/8".
1/2" means more wort in contact with coolant than the 5/8" - increasing cooling efficiency. Enough to overcome the copper vs. steel efficiencies? Probably.
Stainless is also more durable, easier to clean/sanitize, and lets face it, looks better.
The fact that the stainless unit is cheaper is just the icing on the cake for me.