I agree with Graham - nothing beats listening for yourself. I prefer 4000s - I think the bass is better and they are more convenient. I don't think either are great speakers though. The 4000 is good value (for B&O).
If you are after good sound from a small speaker, the Beolab 3 is very nice but I would suggest that for a big room, I would look elsewhere. Get your dealer to give you a good demo - I am sure he will be happy to do so.