With VMware you can add extra CPU cores to give your VM more processing power. I presume you can do the same on Parallels.
However, I do not know how CPU intensive your applications are. So maybe you are just better off with a Windows based machine for your work, but only you can make that decision.
MATLAB uses a lot of computer ressources, it's true...... but I do a lot of thing on the computer, I've done a balance about it and iMac fits my need because:
-I can use it like a PC, the proccesor is 4-core and enough powerful for my use.
-I need a very-good screen and i'm not disposse to use two screens and things like that. By other side I don't have space to use another thing instead of an all-in-one.
- Others models of all-in-one of the competence are less powerful or they are even more expensive than iMac.
-A notebook is not an option at all
So I'm not going to use a PC nowadays.
I'm trying to avoid doing a partition with windows, I think I will try to use VMWare if VirtualBox does not work right...
My last option would be doing a partition