I'm NOT a Menzerna user, but I'll extrapolate from my experiences with other polishes and AIO. If *I* had to choose only one (and I sure wouldn't like that!), *I* would use the abrasive polishes. While AIO's cleaning and oxidation removal abilities are very, very good, I just can't see doing a great job without abrasives if a finish is so neglected that it's oxidized. Abrasives will remove oxidized paint, while AIO will NOT (always) remove other paint defects that are probably there too. SO I'm going with the product that will do the most work.
I'm sure someone will give the OTHER opinion, and with good reasons, so weigh all your responses based on what you're dealing with.