With a shared hosting account the control panel is all about personal preference and features required. Cpanel has more but is also a bit more confusing for a novice user. For shared/reseller Cpanel sells quite a bit it seems.
For a VPS, Cpanel is quite heavy with required memory for it to just install so Plesk would allow the VPS to have less resources and still perform excellent. I would recommend Plesk for a VPS at the VPS M level but we do have many on the Cpanel VPS M and they are very happy. The thing to always remember is you can add RAM as you need right from the control panel (billing system). Feature wise Plesk is getting closer and closer to Cpanel so if I would recommend Plesk as it is easy to learn, use, and navigate.