Light weight wouldn't be my priority for a bike used to haul groceries. A hybrid type bike with longer wheelbase will be better balanced for hauling groceries, etc., regardless of weight. One reason I've kept my Globe Carmel was because of the long wheelbase and low center of gravity, making it more stable when loaded. It feels lighter than it really is when loaded with up to 50 lbs of stuff.

Occasionally I'll use my lighter weight, sportier Univega hybrid for hauling groceries, cat supplies, etc., but it's always more demanding of attention, especially on gravel.

I've never tried to put a rack to haul even light loads on my road bikes. I know the balance would be awful. Occasionally I'll wear a backpack but that's about all.

If I planned to use one bike for everything, including errands, I'd get a drop bar touring bike. The longer wheelbase would help, especially the longer chainstays for the rear wheel to allow more heel clearance with panniers. Getting weight lower in panniers, rather than stacking stuff atop a rack, helps with balance, especially on lighter weight bikes.