I have iPhone's, iPad's, Air, Macbook Pro's, 24" iMac and 27" iMac.....
If i could only have one machine it would be the Macbook Pro. It's the machine i use the most and with the upcoming updates with Lion it'll be even better !
If your wanting to edit loads of videos and Photos then an iMac is really much better but if it's just occasional heavy use i'd stick with a MBP.
My 2p worth !