As solo drives they're not bad actually.
The drive block has very simple controls on its own, just Drive Mix and Volume, but the C4 also gives you Bass and Treble controls and SA's LoRetain outside of drive blocks for further tone sculpting. You could apply pre or post EQ somewhere else along the signal chain to get even more mileage out of the engines too.
Personally I haven't made any isolated Drive presets just because I have an Aftershock next in line.
I was actually considering diving in at some point and isolating the Drive engines to see if the C4 could stand as a drive pedal. I did enjoy Foldover, Single Clip, and the low gain overdrive tone when I was familiarizing myself with the C4's different blocks.
I've said it before but, imo, the C4 is a REALLY impressive solution as a MultiFX unit if a person had to choose only 1 pedal to work with.