Scroll through a large picture that exceeds the amount of VRAM on your gfx board (=swapping data over the zorro bus) and the 4000 will perform a little better.
One real world scenario where the A2000 really fails at in RTG use is flipping high res / bit depth screens. Once you have more of those screens open than will fit in the RTG board's RAM, you will be waiting seconds for the machine to move the new screen into the RTG board.
I happened to have a beefy A2000 and I endured this for a while, but quite soon I became so annoyed with it that I dismantled my 060 + RTG A2000 and sold the pieces, went back to using Zorro 3 Amigas. Haven't had an RTG equipped Zorro 2 machine since.
