I did this for many years. Excel is a company with reliable traffic, but crap pay. Now I actually need money, the phones weren't even considered as an option for me...very poor pay, for a loy of work!
Although if you can build up a customer base on AW it could be very worthwhile 
I used to work for Excel. Was often on the leaderboard, but they 'fired' me!! hahaha....I argued about the pay and poor management. Even though I was one of the best ops (I'm not big-headed, I just found phone sex easy), it wasn't enough to safegaurd my position. And at 18p per min at the BEST rate of pay, I wasn't terribly bothered. I really should give it a go with AW. Miles better rates of pay.
However; the first time I logged on there to work, I only logged off after I'd earned ?250. It took two and a half days without sleep. I wouldn't recommend it unless you're in a bind and desperate for the cash. Friends who still work there say it's gone downhill, lots of 2 minute wankers which make it a really tough job to do for about 14p a minute in the day.
From what I've seen, AW looks the best place. But I'd cut my teeth with excel where it won't ruin your rep if you falter for the first week or so.
Good luck!
Janie x