I use Selinux on all my servers. Never had a problem, it is very easy to define solid security rules. You are right about the PHP flaws. However, those flaws appear ONLY when a programmer write BAD code. It is not PHP's language fault if the programmer knows nothing about coding. IMO, using Suhosin to prevent/correct an eventual mistake a coder can do is not a solution. Plus you know the patch is slowing down the code execution... a little but still does it.
There's a reason selinux is disabled by default with every major control panel install out there.
Any server admin I know will not touch with a 10 feet pole a control panel, like CPanel and other similar software. However, you are the server admin and you decide what is best for your box.