I don't fly for either but with what's going on with ASA I'd choose Republic. ASA's not growing and if they do it's down the road a ways with a few obstacles in their way. Looks like RAH is at the beginning stages of gearing up for their growth so going there would net you seniority relatively quickly. QOL is key but seniority greatly improves any QOL you might expect. Seniority can determine days off, weekends off, holidays off, efficiency of trip, commutable or not and many others.
My advice is to take the seniority (RAH) but remember every changes and nothing's a sure fire bet.