Thanks for the replies!
The point that MXR Octaver has a wider range of sounds is very intriguing, but the one thing I've been mostly concerned about is if the MXR tracks as good as the OctaBass and it was answered

. Next weekend I also have a chance to test the older OctaBass model and I think I might get it (though I've heard it's not as good in terms of tracking as the newer model).
The Aguilar Octamizer seems like an interesting one though. The problem is I've never seen any Aguilar pedals in any music stores in Finland so I have virtually no chance of testing one.