I've never camped at Grant Campground but have camped at Bridge Bay Campground numerous times over the last 36+ years. With the exception of the bottom 4 loops (A- D) it is my most favorite campground that takes reservations. While the lake is across the road, the shore is easy to drive to and there are a few trails you can use to walk down to the shore. Loops A- D are in an open field with Loop A-C mixed use and Loop D tent only. Loops E and F are tent only with some decent views of the lake from Loop F. Loops G-H are mixed use campsites in the trees with no views of the lake. My absolute favorite loop and the one I request is Loop I which is tent only and very secluded. I usually request campsite 424 or 425 and while there are never any guarantees, I've always been able to get them. Loop J is in the trees and is a Group-Hiker/Biker Tent only loop.
Campground map of Bridge Bay Campground *also has some pics
http://www.yellowstone.co/maps/bridgebay.htm
Campground map of Grant Campground *also has some pics
http://www.yellowstone.co/maps/grant.htm
Trip Advisor has reviews for each campground that include lots of pics.
Bridge Bay Campground Trip Advisor Reviews/Pics
https://www.tripadvisor.com/Hotel_Review-g60…
Grant Campground Trip Advisor Reviews/Pics
https://www.tripadvisor.com/Hotel_Review-g60…
IMO, Grant Campground would be ok for touring the southern part of the park including the Old Faithful Geyser Basin but 45 minutes it takes to drive from Grant Village to the Fishing Bridge Junction is a long, sometimes boring drive especially if you have to do it multiple times during your stay. Bridge Bay is 4 miles south of the Fishing Bridge Junction which takes maybe 5-10 to drive depending on the traffic. From Fishing Bridge to the middle of Hayden Valley plan on another 20 minutes (maybe longer if you get into a bison jam). If you're looking to optimize your chance of seeing wolves and grizzly bears staying at Bridge Bay will give you the best chance.
Deb