Unfortunately, or fortunately both Halcyon and DSS (I use both) are of sufficient quality that trying to find enough fault with one or the other to make a decision, would just be unnecessary and fruitless nitpicking.
Again, unfortunately for helping your decision, but fortunately no matter which you choose, customer service wise they've both been great. . .
With Halcyon I had to deal with them over a bad OPV spring recall and the way they dealt with it was fine by me. I called and said I had one of the bad springs and they asked me if I had the serial number for my H2, I said "no, it's at my place in Mexico and I'm here in the U.S., does it affect me getting the spring?" They said "no, what address should we send the spring to?" I told them my address, and a few days later the spring arrived in the mail.
With DSS I loaned them my VT3 computer to use for making the mold for their rubber boot. I got it back quicker than I thought I would and in exactly the same condition, but, with a free boot, a t-shirt (what he said he would give me for loaning them the VT3) as well as, a SMB reel w/line and a stainless steel double ended snap link. Tell me that wasn't cool of him.
Good luck choosing!