I'd go with the 1/2oz ... regardless of weight of jighead. I use 1/2oz on a single jig rig, for "pushing" jigs ... and may use 3/4oz to start off this season, just to see if there's any great difference. My spider rigging buddy used to use 1/2oz egg sinkers & recently switched to 3/4oz in line trolling weights (torpedo shaped). He uses a leader line with a single jighead, 2" plastics of various colors/brands/shapes, and tips with a large minnow.
I'm not a big fan of "double rigs" ... due to all the hardware on some of them, and having twice the chance of getting snagged in the cover. It's not "too hard" to get one hook popped off a tree branch, by dropping the trolling weight below the jig/hook ... but, when there's another open hook flopping around, it's very likely to also become snagged when attempting to free the other. Now, they may be OK for use in open water, on suspended fish ... but, around brush piles, you're asking for trouble IMHO. And if they were "more likely" to catch two fish at a time, most of the time, you wouldn't hear of very many people using the single bait rigs.
... cp