i own and ride both as well - honestly, i run the clips for anything with speed, they give me far better control on the bike as to the position of the rear wheel, hopping, pedaling, all that... As for my flats, i run those when i ride my home trails or im hiking, mostly because i purposefully find it impossible to keep my feet on, with flats i have no intention on going fast, i just want to drag bar and foot and hold it as sideways as possible. So pretty much, flats for messing around, clips for actually trying...
i run shimano dx clips and Point1 Podium pedals, both are the best... i ran mallets for 4 months before i snapped the axle, crankbrothers wouldnt return my calls when i called to try to buy replacement parts even though it was under warrenty, ponied up for the dx's and i couldnt be happier...