If you're talking about an HOURLY win/loss rate, you'll also have take under consideration what you're trying to accomplish. If you're counting and you want to slap a $2.50 chip on top of your bets; of course; you WILL be gaining an extra 25c four or five times an hour, but at the expense of slowing the game down because of the dealer having to break your bet down every hand. This could end up costing you more than the buck that you THINK you're saving.
However, if you're a basic strategy player, slowing down the game is a GOOD thing (provided you don't mind pissing off the other players).