Ha ha never even noticed you had said Mach2.
Suppose it really depends on you, if it does all you need and works fine then you may be happy to stick with Mach2.
Personally I would go to Mach3 but the good thing is both Mach2 and Mach3 will happily live on the same computer, obviously you can only have one open at a time, but it allows you to try Mach3 and if you dont like then you can easily just shut down and start Mach2 up again

You will have to configure Mach3 manually as the xml for Mach2 is no use for Mach3 and vice versa.
Hood