I think I'd go with two guns, one bigger gun that stays in the car and one smaller gun that gets carried when you leave the car. I think I'd try to keep the ammo the same so I'd go for a Smith and Wesson 686P with a 4" barrel for driving the car to the grocery store and a Smith and Wesson M&P 340 for walking to and from the grocery store. That's just me of course. Opinions will definitely vary.
7 rounds of .357 magnum, dependable, extremely authoritative
Five shots of .357 magnum, tritium sites, dependable, extremely concealable
I really like that 686 in your picture.
I'd prefer that over a shotgun for home defense. Also makes for a great car gun.