It's a Honda self-propelled model I got two yrs ago. It does a good job of mulching, has four cutting edge blade to aid more effective mulching.
What got me started bagging this year was a particularly bad out break of dandeloins that were in seed mode. Those freakin stalks were everywhere. Sprayed lawn w/ Ortho Weed 'B Gone. Mulching would only have re-planted all those seeds even after weed killer wilted them, so I wanted to suck them and other weeds up into the bag and not "replant" by blowing their seeds down into the lawn.
Been bagging since. Probably switch back to mulching in a few weeks, on you guys' advice, now that the weeds are under control. Seems reasonable.