Maine Road was hardly used bar MU v OA, MU v Liv, Liv v Everton in the last 50 years. If there were replays they would be on a different ground, normally the one that travelled the furthest for the first game would have it closer the 2nd, and the 3rd would also be different and pitches couldn't take it.Villa was way better by all accounts - also its a traditional SF ground, they had Hillsborough, Maine Road, Villa Park I think Arsenal, occasionally Anfield and occasionally the swamp - Should get back to this for the Semi's as Wobbly has been paid off (surely!!) or is the Dartford Bridge crossing syndrome - another never ending money earner!
All semis and finals were at the Oval to start, but mainly SE teams, and then the final moved to Fallowfield (yes Manchester) for a few seasons. Most midlands grounds have had semis, but it settled down to mainly Villa Park, Highbury and Hillsbro since the 60s before OT took over then Wembley.
Villa Park isn't fit for purpose, it is an old dangerous ground when we visited in winter with slippy narrow steps and tiny concourses. Not that some grounds nearby are any better.