2 bikes:

A) road bike for nice days and days where I'm not carrying cargo. No rack, no panniers, no fenders. I do that up to 4 days a week.

B) 15 year old hybrid bike I call 'Sherpa'. Steel frame, probably 30 pounds or more. Rack, fenders, 700Cx37mm tires. Once a week, I haul all the crap I'm going to need all week (clean clothes, lunches, snacks). Also use it for bad weather conditions which will probably include most of the winter.

I heartily recommend the 2-bike setup because trying to get the 'all-in-one' bike results in too many compromises in my opinion. And the cargo hauler doesn't need to be expensive - no point getting all weight weenie with a bike that you're about to lash 20 pounds of cargo to. $100 or less for an old bike plus about the same in Nashbar upgrades and you have a very serviceable sherpa.