It all depends on what size engine you have too. If you have a big bore/stroker engine (like me), then you'd want a set of LCBs with a bigger bore width. I'm using crappy ol' 3-1s at the moment, and whilst it runs beautifully, it doesn't quite have the power it should, especially when you put your foot down. Plus, my cam's power range is from 3500-8250 revs, and my car loves it around 3500-4000. Since it loves these higher revs, it would love a bit more from the extractors.
If I was you, I'd probably ditch the 3-1s and get a set of LCBs with a small bore width, which is basically the best of both worlds if you have an 1100 or something.
Oh, and when I refer to 3-1s, I mean the ones that join together high up, found on older Minis, and NOT the hardcore racer 3-1s which join up underneath the chassis and are wide enough to stick your fist into.

LOL!