Two volume controls would always be better than one and a balance pot. It is however a bit more fiddly to adjust the levels. Here is a trick I saw Steve McCormack demonstrate at a High Fi show: He set up a preamp with the two volume pots connected with a friction string system like on an old school tuner. You can let them turn together while just moving one, or adjust them seperately if needed. I'm thinking "why doesn't everybody do that"
