I would pick the Triumph, but I have never owned one (yet ).
I have owned an Omega, and it was very accurate with a variety of bullet/sabot combos, but the triumph should be easier to clean, and cleaner to shoot.
Not wanting to offend, or start any arguments, but my most recent Knights I've ownedhaven't been the quality of the older models I've owned, and my last dealings with Knight's customer service didn't satisfy my expectations. Trivial problem with screws that were too long, but "just file 'em down" wasn't the answer I expected!