Planted Tank Guru
Join Date: Jan 2010
Location: Contra Costa CA
The difference is often price.
The most commonly available Oto is cheapest. They are very good algae eaters.
More expensive ones like Zebras are good algae eaters, too, but not better, unless you are looking for the unusual coloring.
Similar in size to Otos are Paraotocinclus and Pitbull Plecos. Any of these can work in tanks as small as 10 gallons.
Larger fish that are 'best' for algae are Rubber lips (20 gallon minimum), and larger than them are Bristlenose Plecos (40 gallon minimum). There are several species of BN, and some variations like albino and long fin. These variations are all good for algae. If you have access to some of the more unusual Ancistrus (Bristlenose) I am not sure how each one ranks for algae, but they sure are interesting!
Look at Planet Catfish for more info.