GTO has very good quality minnows. I don't know that the minners are better quality but they're kept in better conditions and they have them all year. There's no telling what their water filtration system and chiller cost.
Alder Springs grocery in Alder Springs has good minnows but only keeps them in the cool months as does Perry's store on 227. Ms Perry is a nice old lady and I like to buy from her because she's not doing a whole lot of business anyway, but she babies those minnows. All 3 of those places sell by the 1/4, 1/2 or pound. They also sell them by the dozen if you want to buy them that way.
The store at South Sauty keeps minnows most of the year and they're pretty good quality too, but you never know if they've got toughies or 3" shiners that they think are toughies.
The foreigner owned gas stations around Guntersville have minnows, one at 79 and 431 intersection and one on 69 on the west side of the causeway. Their quality is terrible. They use so much blue stuff in the water to make up for not changing it often that it's hard to see the minnows in the bucket. Even in cool weather they won't live all day with a bubbler running.