If performance figures were relative to balance or equity, a rich guy with much money on his account would get a different performance than a poor guy. You normally want to know the performance of your strategy, not of your account.

The exception is testing the money management. Then you really need metrics relative to equity, such as the CAGR. For this set up the "Capital" variable. All metrics change then their meaning. Read the "Performance" chapter - all is explained there.