I wrote a quick comparison of the two releases at:
http://www.archerytalk.com/vb/showthread.php?t=380352
Since I had written the above comparison, I have rebought another Loesch and prefer it over the Evolution, only because it fits my smaller hand better.
Some new things to add in my comparison is that the Evolution has a "crisper" release then the Loesch. And the Evolution does not protrude as much as the Loesch so you will give you "more drawlength" for the same anchor point.
But I like the Loesch just fine. (Not willing to give up my Evolution quite yet though)
Bottom line: get the one that fits your hand. Both releases utilize the same concept for release which has worked out to be the best I've found so far.
Good Luck.
Sam