h22 obviously has more displacement thus creating usually a decent amount of tq over the 18's, but they don't have as much aftermarket support as B series motors do as in terms of cam choice, pistons choices, etc..
They cost cheaper than teh b18c but then again you must buy a mount kit for the motor to fit, they are also heavier "not by much" than over the B series motor.
But, like E said it depends on what your car is goign to be doing, what type of funding you have, etc..