This is difficult call. The PHX-SMF (and return) would give you excellent chances for upgrades, but the PHX-CLT would not, as it's mainline, hub-to-hub and full of CP's.

SMF-PHL would have higher chances than the above PHX-CLT, but it's hard to determine for certain. PHL-CLT, while hub-to-hub, I don't think would be much of a problem since it's a plentiful route.

What days are you looking at?

HTSC