Reserve at PSA is a special type of hell. The LOA didn't improve anything and in my opinion made it worse than it was before. You'll be on reserve definitely for the first year.
With that said, SAP is apparently awesome, can't personally vouch for that, but all the line holders love it.
Commute to CLT will be pretty easy for you and CLT isn't going anywhere for PSA.
With that said I kinda wish I went to Republic. They announced a base in my home city six months after I got to PSA. A well. My friends at republic are flying more at Republic than me, but once I'm a line holder it won't matter.
Now the flow.... I don't really care for the flow right now since it's 8-10 (I don't honestly know how many) years away from me. So far that it's essentially not a factor. Also FOs aren't eligible for the flow. With that said it's there and it's a great back up. I think the flow will get adjusted so that more are flowing so that'll change the times to flow. AA wants it, it's just PSA is dragging their feet.
Both are good companies, I think republic has a little nicer contract and better work rules. But once again the grass is always greener.