I want to get a set of punches to disassemble a 1911. Is there an advantage to those with a convex tip vs a flat tip?
Exactly. The only exception to that would be some rear sights that are installed with a roll pin, but the only reasons for removing these would be a sight change or a refinish. With that said, it's still a good idea to have roll pin punches in you tool box. As a matter of fact, the smallest installation punch in my Brownells set is the perfect tool for installing the trigger spring in a Colt Mk III action...At most, you only need two punches to disassemble a Colt 1911.
One size to fit the mainspring housing retention pin, and one size to fit everything else.
A 1/8" inch and a 1/16" inch flat face will do everything.
While the 1911 can be disassembled without tools, a couple of punches and gunsmiths screwdriver bits to fit the grip screws and the magazine catch lock save scratching up the parts.