The average size of a Publix in GA is 47,334 SF (and 151 of GA's 182 Publixes are in the Atlanta CSA). There are only 7 Publixes under 30,000 SF, and almost all are in the Perimeter of Atlanta. 2 of them are built in the last decade.
Pre-1970 size = 39,928 SF (6 centers)
1970s size = 39,344 SF (7 centers)
1980s size = 45,339 SF (13 centers)
1990s size = 51,062 SF (too many centers to count)
2000s size = 45,187 SF (also too many centers to count, but fewer than in the 1990s)
Keep in mind many of the 1960s, 70s, and 80s stores have expanded and remodeled since that time, skewing their numbers (i.e. they were probably built smaller than their configuration noted now).
GA and FL Publixes are exactly the same.
The average Kroger size in GA is 59,032 SF. There are 163 Krogers in the state, and 129 of them are in the Atlanta CSA. There is only 1 store under 40,000 SF in the state (though my data is missing a chunk of information for Krogers...had all the data for Publix).
Pre-1970s size = 56,683 SF (I only had size data for 2 centers and only 3 centers total that old)
1970s size = 60,575 SF (14 centers, not all centers had size data)
1980s size = 53,451 SF (lots of centers, missing a good bit of data, though)
1990s size = 60,723 SF (lots of centers, missing a good bit of data, though)
2000s size = 61,513 SF (lots of centers, missing a good bit of data, though)
Average age for Publix = 15 years
Average age for Kroger = 19 years
Largest Kroger = 92,803 SF (with 40 over 60,000 SF, largest built this year, 60,000 SF + built since 80s)
Largest Publix = 65,495 SF (with 5 over 60,000 SF, all built in the late 90s and 2000s in suburban areas)
Largest Publix in the urban core is 40,000 SF in Atlantic Station, built 2004-2005.
Urban Krogers are fewer and farther between than urban Publixes (still 2 in Midtown alone), but they range from 41,000 SF to 56,000 SF.
The only other grocery stores that matter for institutional capital are Whole Foods and Fresh Market. Perhaps a Trader Joes in a wealthy infill neighborhood. There are 9 Whole Foods in Atlanta and 11 Fresh Markets. There are 7 TJ's in GA, 6 in Atlanta, mainly in the core and inner suburbs, and 1 in Athens. Aldi's is also really big here, but is nowhere near institutional grade. I won't even get into stats for these grocers.