I agree, if you have a serious case of algae, try to determine the cause and then fix it. If you just have little spots of algae on the glass here and there, an algae scraper is a better option that getting a fish that will need extra feeding and add to the bio-load (especialy since this is a discus tank).
Having said that, if you need to choose an algae eater, you need to first look at what kind of algae you have. SAEs will help with red algae which most other fish won't and they'll also eat the other types as well as any pleco, but, as they are active schooling fish that get quite big, they can be a stressful tankmate for discus and you have to get more than one.
If you don't have a serious problem with the algae and just want a fish that'll graze on it to prevent it from getting too bad, a flying fox would work (but these can be a little aggressive) or you could try to find a false SAE (garra taeniata) or a short-nosed FF (crossocheilus oblongus). Any of these, kept alone, would do well and they aren't quite as hyper-active, spending most of their time near the bottom of the tank.
Alternatively, american-flag fish will also serve the purpose of keeping algae from spreading and are not aggressive towards other fish. They also stay small and have some very interesting behaviours + are easy to breed.
If you want a fish that'll clean up all your algae but also stays small, otos are the way to go. Just keep in mind how fragile they can be and make sure they always have good amounts of veggies or spirulina to eat. They also won't appreciate very high temps which most discus require - so only keep them if, for whatever reason, your temp is 80 deg F or below.
Plecos are generaly not reccomended for discus tanks though I think the possibility of them causing problems has been exaggerated somewhat. If you want a plec, bristlenoses and bullnose/bulldog plecs are probably some of the better algae eaters. However, watch which species you get (especialy with the bulldog/bullnose) as some don't tolerate high temperatures well and some require wood in their diet (bristlenoses don't). Another that you could perhaps consider are farlowellas - though I'm not sure about their temp. range tolerance - and I would expect that concerns about keeping plecs with discus would not extend to farlowellas.
edit: concerning the fish you were considering, without scientific names I'm not sure what each of the plecs you mentioned are. However, the sailfin and the 'chocolate' are probably species that get much too big for your average tank.