Sorry for the lameness in advance

Going IAH-ATL on Sunday, but I need to change my flight
I am looking at flight 1420 10:40am-1:43pm flight.

I can Y-up for 77$,
I can SDC for 25$, or
I can stand-by for free. 77$ to roll in F is good, but it is only a 90 min flight. SDC will probably allow me to avoid a middle seat and that's reasonably good. Stand-by is of course free and I would probably get a middle seat.

So what is my best course of action? How much is this segment worth?
*straps on the flak jacket*

TYIA.