Headed to Port A/Corpus and have fished most of these piers before. I have caught some at Red Dot and a few at Caldwell...just looking for the best chance at some specks n reds at night specifically. Headed down there this weekend with some sabiki rigs to catch bait and the usual assortment of artificials...only chances I really have to wet a line is after the littluns crash for the night...so what's your ranking?
I haven't yet fished Oso or Conn Brown Harbor, but I would rate the others in the order of Red Dot, Caldwell, Bob Hall. Have heard good things about Oso and Conn Brown though.

Bob Hall: Caught my biggest specks between light 1 & 2. Reds on live bait, freeline if possible.
Caldwell: Have caught some nice specks within the first 3 lights.
Copano Bay Pier: Have had luck at the first 2 lights with specks on artificial.
Fulton Fishing Pier: Love this pier and the green LED lights. Grew up fishing this pier all night long and catching specks, sheephead and black drum.

This is just a few. Honestly I would roadtrip it all night when I drove down from SA. I would start at Copano and pier hop all the way till I got to Bob Hall. Some good times and good fishing.

JJ4mel is on the money for Horace! I catch specs all night long between 2nd and third light on right as you walk out to the end of the pier! 10pm-2am or later every time I go.. freelined shrimp on a #2 treble.. is king no doubt! Just be careful when you set the hook and miss! That treble gets airborne quickly in the wind and could be dangerous! Freeze some Gatorade bottles,get you an aerated bait bucket go to port a outfitters before the close.. get your shrimp! Use the frozen bottles to keep them cooled as you wait for that late night pier trip! This rips lips 100% of the time for me!