Mid-weight all the way. The FQHH is 3.0z thick - not all that period accurate - they generally used lighter hides in the old days and heavy hide is not as versatile or comfortable as lighter hide. I get nothing heavier that 2.5oz which I have come to after 30 years of collecting and handling leathers. Goat is great because it is really tough and light.
You simply don't need the FQHH unless you're on a bike. And it's not just about it being Horween horse. I find steer and cowhide at that thickness by the other tanneires as unappealing, even when soft and flexible. Sure, you can wear thick hides and enjoy their looks, that's fine, but you don't have to and you may well find as I do that lighter is more comfortable and enjoyable.
And remember heavier hides don't keep you warmer in winter - it's the layering or the lining that accomplishes that task.
I have tended to go with FQHH which itself has quite a bit of variation in weight and thickness (at least that's what I've seen over the years). I'd definitely consider a lighter hide if / when I got another jacket. I've not seen many original jackets but from what collectors say, the very heavy stuff wasn't used.