My new TSF Beast is phenomenal. When it first arrived, I didn't care for the sharp edges on the frame (it is designed with them for better grip when wearing combat gloves), and the blade sat a touch high when closed. I emailed Jim back, and he said it was a quick fix (minutes). I mailed the knife to him, and he rounded and smoothed all the edges and then refinished the frame, and also dropped the blade 2mm. It came back in less than a week and even better than when it arrived.
Given really close inspection of the TSF Beast and the online reviews/pictures I've seen of the Dua, the TSF is more finely finished. What some object to are the sharp edges, but all that can be customized, it only takes an email to Jim. The blade is beautifully ground and came shaving sharp--I also think the steel is better. Lockup is perfect, everything is perfectly centered and it's incredible strong (no blade play, obviously). Mine also has an extra strong detent, which I like, and it flies open. It's incredibly smooth (Jim is using bushings now, not the IKBS, for durability reasons).
At any rate, I recommend the TSF. The Dua looks interesting, but given several reviews I've seen, the quality control seems problematic. They are also more roughly finished--why would you advocate for the rough sharpening? I want a knife to actually cut, not chop, and the TSF slices beautifully, despite the thick blade. I've been using it to slice ripe tomatoes the last couple of days--can you do that with a Dua? ;-)
Order both, compare them and then send the one you don't like back--both have great return policies.
Cheers,
Daniel