I have been reducing my 3rd party security software as time goes on, for a few reasons.
1 - The security industry are starting to get silly with pricing, the products that will still be genuinely an improvement over windows defender charge silly pricing for consumers.
2 - The issues with various of these software's especially the ones that are always on hooking into programs, have over time caused me compatibility issues, like unexplained memory leaks or crashes.
I still have nod32 but it wont be on my machine once windows 10 is on there in a couple of weeks, nod32 has always been my go to for the reason already stated in this thread, its one of the few a/v that has a very low overhead and you dont really notice it.
Now days its basically my own hardening configuration, combined with utilising built in memory exploit protections, that is one of the good things about windows 10, it has been significantly hardened. Remember EMET? that's now part of windows defender.