It's tougher with the 5 gal as the betta or shrimp/ dwarf frogs would be the only good candidates there. Thats what i think. other members should try and fix my opinion if they think it fit.
The ten gallon can give you more options in terms of actual fish, but then again youre still limited to small fish the size of guppies and neon tetras.
Other recommendations for the ten gal include:
Snails
Platy
Pigmy cory
Peppered cory
Zebra Danios
The smaller Barb species
Oto's (otocinclus)
The smaller Tetra species
You want to avoid getting fish that reach an adult size of more than 1-2 inches.
I hope i helped somehow