Do you mean the micro VR an CL stacks? The biggest difference I saw was that the VR (the classic SVT-looking one) had a gain control whereas the CL has an Aux level on the front, and only a master volume.
I've tried both, and was unimpressed. There is no real low-end to these things and yet the treble is also strangely missing. These things basically deliver a chunk of punchy mids. Imagine an SVT coming down an AM radio. I didn't notice more overdrive when I wound up the gain control on the VR either, just a more frantic and pushed sound from the drivers.
Honestly, you can get much more efficient, far better designed amps that work well as bass practice amps. I'm glad I purchased my Fender Rumble 112 out of the half dozen different amps I tried. The wee Ampegs look the part but don't sound good. If they weren't branded Ampeg they would be much cheaper, and I don't trust Ampeg's reliability with this sort of stuff. Ampeg could have been a bit smart, and used the sort of technology in Phil Jones or even the Yamaha THR amps to deliver big tone from a small footprint. Rather I think they focussed on the aesthetics, and spooned a fairly lacklustre 'vanilla' practice amp circuit into the head, and then used a somewhat generically designed sealed 210 cab to complete the picture.