Usually a simple system is the best system. When several variables take place in a single action, usually several rolls fix that problem. I have played with a few rule systems and some are aggravatingly annoying while others are great. I personally really like the percentage system, but the World of Darkness is also fun, albeit lacking in many more "advanced aspects", however as I mentioned, in the in depths situations in for example a battle, more than one or two rolls with more skills usually get through.