The biggest delay in BRS seems to be the ramp. The terminal is fine, runway often empty, & then everyone wastes ages with buses all over the ramp. The process of getting people to & from the aircraft just hasn't been thought out.
SOU has the problem of a short(ish) runway & the necessity of having to taxy on the runway. Not much room for expansion either.
Both airports have grown tremendously in the last few years so the demand is clearly there.