I bought the Legend LX Supreme last year, & I love it. I went w/ the supreme mainly for looks, as all my equipment was black/blue/ & grey it looked nicer (I also like the idea that if I wanted to I could dive in freezing conditions). I like having the extra knob, as I make a lot of surf entries. I turn everything down because I've been knocked over, & had the reg. torn out of my mouth. With everything turned down the reg hasn't freeflowd. Then I adjust the reg. when conditions permit.
I have also used the Scuba Pro Mark25/ 600 reg. It is also a good reg. worked the same. The mouth peice was a little more comfortable, & the 2nd stage was a few ounces lighter. However the The Legend LX Supreme felt a little sturdier to me, but my opinion on the build quality, is just based on feel.