I had the same choice to make earlier this Spring after becoming fed up with the goldtip outserts and then drawing a Bull Moose tag in idaho. I wanted something more reliable than the GT, heavier than my current set up of 442, and needed a fixed blade BH to comply with Idaho regs. I pretty quickly narrowed it down to the same two choices as you have.
The cost is high on either system, but I believe the Valkyrie system is a fair amount cheaper (might want to validate that).
I really like the 2 blade, single bevel heads from Grizzly Sticks and the research that it's based on, however I went with the Valkyrie system b/c of their center pin system and I've been very happy with them.
I was worried about the reduced speed and pin gaps resulting from a heavy set up, but it turned out to be a non-issue.
I ended up with 225gr heads and a total weight of 496gr. 28.5" draw, 70 lbs. 269ft/sec. I shoot the axcel 5 pin slider and I really didn't see a discernable difference in pin gaps. In fact, for longer ranges (70-110) where I'm dialing down the site, the gaps are actually smaller. My assumption is that the FOC helps them carry better at distance.
Anyway, I think either choice is a good one and luckily both companies have an inexpensive 2 arrow test kit that you can order with various heads. This allows you to see what combo your bow likes best, and if you take advantage of that it should help make the decision much easier.
I'm very happy with the Valkyrie. I was able to put 2 of them through moose a few weeks ago. 1 broadside at 35ish, one quartering away at 22. Both were full pass throughs and neither arrow was ever found. That's good enough for me!
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