TGPR should be used it you are using only hosted and / or your own galleries.
Now, the differences between AG SQL and AG Pro can be significant, or they can be nothing depending on your needs.
Scroll down to the feature list here:
http://jmbsoft.com/software/ags/ and the items and blue are things AG SQL offers above and beyond AG Pro.
Edit: the additional scanner features alone make AG SQL the smarter choice for the relatively low extra cost.