I have both, a Seaquest Balance and a Halcyon 36 pound wing. The biggest difference that I can see is the Halcyon provides more flexibility at the cost of being harder to set up. You can take the Balance out of the box pull the straps tight and be ready to go. I spent two hours a day for three days adjusting the harness on the BP& W and Im still tweaking it. However, after spending that time, the d-rings are where I want them and the weight pouches are where I want them while theres no adjustability with the Balance.
I also like the doughnut shape of the Halcyon bladder better than the horseshoe shape of the Balance bladder. The horseshoe shape allows air to get trapped in one side with a head down orientation. Not that its a big deal, you learn to go vertical to dump air and it becomes automatic.
The Balance has more padding and that causes more drag, the first difference I noticed when I got in the water with the Halcyon is that it took less effort to start moving.
I think that you have made a wise choice going to back inflation, but I caution you that it is going to feel strange at first and it will likely take a few dives to get your buoyancy control back to where it is now. If you are expecting to strap on a BP&W and swim like a dolphin you are apt to be sorely disappointed. But at least in my case it was worth the effort.
Which is better for you the Seaquest or the Halcyon? I think that depends on how often you dive. If you only go on a couple of trips a year I recommend the Seaquest, it works well out of the box. However, if youre addicted to diving like I am, I recommend the Halcyon. Its a pain in the ass to set up but once you get it, its well worth the effort. Whichever you choose make sure you get some pool/quarry time before you go on a trip or you might spend the trip getting use to it rather than looking at the scenery.
Mike
but seriously I am really considering the two most likely Halcyon or Seaquest Help?
