It depends on what you are trying to do. If you are looking at anything systematic where you are maintaining a portfolio of trades based on some rules, you want to look at profit over trade value (in whatever terms - ticks per contract traded, % over notional etc). If profit per contract is of the same order as the transaction costs, it's worth trying to figure out how to reduce your trade frequency (introduce some "flicker control" etc) or change your execution process. High freak guys have all sorts of more scientific methods to analyze this (they also tend to pay more of TCs), but for my games this approach is mostly sufficient.
There are strategies where I am, in general, a taker of liquidity and strategies where I find providing liquidity is an optimal approach. There are negative aspects to both, but it really depends on what exactly the game is.