Did you read the link I posted? The rotary is a totally different machine. It spins a lot faster and it has the ability to burn your paint and create all sorts of problems. If you know how to use one then it can do some pretty amazing things, but if you don't know how to use one then you can really screw up your paint. The PC is a much safer tool and impossible to ruin your paint with.
I wouldn't suggest using a rotary to apply waxes or sealants with. It goes much to fast for that. However, since you said you have been using one for the last few years then you are probably already familiar with how it works. The only reason you would want a PC if you are good with a rotary is so you have a machine you can quickly apply sealants and waxes with.
I don't use a rotary simply because I haven't come across a job that the PC and the right combination of product and pad couldn't tackle. There is just too much risk for my taste with a rotary. I don't really feel like having someone's car repainted because I wasn't paying attention and burned the paint off around every edge or something. But if you are comfortable with one then they are very efficient tools.
