I'll chime in with another vote for the Sabertooth. I picked mine up last year and haven't looked back since. I LOVE it.

As for your question re: single vs. dual caliper, this is what I was told awhile back: Single caliper releases promote a more consistant release because there's only one moving part. The string, or loop, is going to leave the release the exact same every single time as that one single caliper opens. With a dual caliper there is a little room for inconsitancy because both parts of the head are moving, and based upon how you're holding the release (ie torquing it one way or another) it could effect your accuracy. Now whether that's true or not, I really don't know. Just something I was told.

Either way, I'm not sure the difference would ever be something that 95% of us would ever be able to tell. For me it came down to what felt better when I was shooting it, and the Sabertooth won.