Personally, Ensim 4.0.x (which we are running on our servers) is my favourite control panel.

I've used cPanel in the past, and whilst it did have more features (compared to the older Ensim 3.1, at least), it seems quite bloated and hard to use. To me, cPanel has never looked or felt quite as finished off as Ensim has.

From a server administrators side of things, Ensim servers used to be slightly harder to maintain, due to Ensim making a lot of changes to various software packages, etc. If you were to then upgrade certain software packages, you could bet your life something would stop working. This hasn't ever really been the case with cPanel, and isn't so much the case anymore with the new version of Ensim - you now have a lot more freedom to upgrade packages and make modifications, with exception to a few things.

So, Ensim has certainly come a long way, and in my opinion is the best control panel out there. Generally, Ensim is also a lot more secure as standard (and, providing you keep things updated, should be more secure than cPanel). This is due to the chrooted environment under which accounts operate.

In conclusion, for me the answer would be Ensim!