ZZ-b FTW !
Funny that almost everybody here dwells on just having a 3gen F2L with no cube-turns as the main benefit of ZZ (the EO line, that is).
After doing CFOP with full OLL and full PLL, which I learned at sub 75 s (that's correct, Sirs and Madams, and I don't regret having learned it that early) and with which I went to sub 30s (PB:19.5, (3/5):25.7, (10/12):27.1), I figured that ZZ-b HAS TO BE *THE* METHOD!
I'm learning ZZLL right now and have 20/80 unique alg.s down and I started 5 days ago. Extrapolating from my learning experience of full OLL & PLL I assume I'll have full ZZLL down in 6 weeks and in 4-6 months I'll have all alg.s consolidated and in my muscle memory.
IMO, once you master the EO-line and ZZLL, you *will* be faster than with CFOP and for the following reasons:
EO-line takes about 0.8 moves more than the cross and so a tiny bit longer; 3gen F2L in ZZ takes about the same amount of moves as CFOP-F2L (move restrictions in ZZ-F2L being made up by block building possibilities) but will actually be a bit faster because of no cube rotations and being 3-gen. Phasing, including positioning the last F2L-pair, costs about 1.5-3 moves more than CFOP-LS or ZBLS, and the necessary "inspection", if you can call it that, about 0.5 s. And then there's an inspection time for the ZZLL case which is just a little bit longer than for full PLL and definitely shorter than for full OLL + full PLL - which leaves executing the ZZLL alg, which is about as fast as full PLL (~12 vs ~11 moves).
So, in essence, EVERY ZZ-b solve will be about as fast as an OLL-skip in CFOP, on average!
To be honest, the Winter variation (EO-line-3genF2L-WVLS-EPLL, I mean by that - it takes about 8 moves plus the few moves necessary to build the last pair) is almost as move-efficient as ZZ-b (but not as inspection time-efficient, btw) and with only 27 alg.s to learn instead of 160-170. So, if I had to get as fast as possible ASAP, I'd just improve on my EO-line and learn the Winter variation - and maybe the Summer variation as well. But since I have a lot of time on my hands I will commit to full ZZ-b.
I would appreciate your opinions!
P.S. I think that ZZ-a is just overkill (~100-150 cases for ZBLS + ~480 cases for ZBLL) and will likely not even be faster than ZZ-b because of the longer recognition times for the ZBLS and ZBLL cases.