Well, let's see- I ahve always been in favor of Emerald's just becasue out of all the terrible stories I hear about crabs- they are in the least. Also, many people keep them, and if you provide for them correctly, you may not have any problems at all. I can safely say, though, that Emeralds are definitely a better choice than a Salleylightfoot. Now, I'm not speaking from experience, but I have heard many war stories with them, as well as many stories of CBS tearing their legs off- so your CBS may be a problem there.
If the only algea you are having problems with is hair, then hermits (realize some people put as many as 2 per Gallon in their tank- that's nearly a 100 in your case) are going to be a great option for you- although like any crabs you may have some problems with them killing your snails for shells ect...Now I wouldn't recommend 100 hermits for you, and I'm not trying to, but 5 is not enough to make even a dent in your hair algea. I'd honeslty recommend about 25 for a tank your size. And Emeralds, if you can keep them fed and keep up with their needs, I'd say 3.
Good luck, if you have any more questions, feel free to ask!