There are pros and cons to oto's. Pro: They do eat algea. Pro: They don't produce nearly the amount of waste that Pleco's do (I had a pleco, in just one night he/she could cover the who bottom of the tank in poop) Con: Oto's are fragile, if your tank isn't cycled or if the water's not right they will usually die. Con: They don't eat as much as Pleco's so you will need several.
All in all, when I set a tank up again I think I'm going to go with an army of Oto's approach.
Hope that helps.