Hi and welcome to AA!
Will you be using only 1 return? A 3/4" has 660gph gravity flow, a 1" is 950gph. Are you using a skimmer? If so I'll assume your return pump will be rated 3-5x your tank volume flow. Without a skimmer, you can have a higher flow.
Either way I think you'll be fine with either pipe. Is your pipe going to be drilled through the back? If it's drilled I'd go with the 1" pipe and install a ball valve so you can dial it down if needed. If you're using an overflow, I'd go with the 3/4" pipe since it's smaller. A 1" overflow pipe in a 29g is pretty large.