Great topic.
I guess 2000-2500 is favourite because it gets you over the ATZs but below the Airspace without constantly jinking around things.
I personally cover all options by constantly varying height by plus or minus 300ft. If anyone knows how to make a plane stay level when you look away from the altimeter or talk on the radio or put the flaps down or write down a clearance of carry out a freda check I'd be very grateful (and so will my instructor).
If I am flying a cabriolet plane I tend to favour 500-1000' because it is a lot warmer than 3000 and you can see a lot more. Its also quite fun navigating so low and needing to jink around every town you come across.