You will have to try it and see.

Does your car have a cam sensor on either of the cams (you havent said what management you are on or anything like that)? cause if it does, you may find you need to move the other one.

As a general rule though, id sooner move them both a bit than one of them a lot.

Also depends if you want to move the torque up the rev range or down it as generally speaking the more retarded the cam timing is the further up the rev range you will go, so dialling out the lift on overlap by retarding only will move the power up, and dialling it out by just advancing the other cam will move it down the range, so if you are otherwise happy with the engine, thats why i would initially opt for a bit of both instead.