Wasn't this compared before?
There's no better engine. Both engines came with different models for different purposes. If they were limited to the same chassis from factory the comparison would make alot more sense.
Now, the B18c is the platform I'd choose, depending on the chassis and I'm assuming that you're thinking civic. Don't get me wrong the F20B is a great engine, with a rich history of racing also (Mugen 300+hp JTCC car and F3 race cars), but for an all round great performer (READ: great straightaways and superb vehicle handling) it's hard to beat the B18CR in the lighter chassis.
Back in the day, when everyone was running the B series there was hardly any support for the H and F series as they came stock in heavy chassis that everyone shyed away from. Now things are different, a lot of hybrids are emerging now with lots of support for these engines, and all motor H series engines doing low 11's and high 10's in EG/ EK street trim. I'd still choose the B18CR because it can pull similar numbers at the strip based on any relevant combination of it's vast aftermarket support and it's even more nimble around the circuit too. The F20B is also a high revving engine but it was just made for a heavy ass car (Accord SiR-T/ Torneo).
Mugen F20B