I think their are pros and cons for both tbh.
I personally like to offer a wide range of treatments, although they are generally on the same theme, ie massage, energy treatments, but have recently taken on a named company and offer facials and body treatments too.
what I like about offering a lot of treatments is that I can 'dip' into a variety of techniques if I feel its needed, so if I was doing a massage, I can dip into Swedish, aromatherapy, hands-free, Indonesian, Indian head, tibetan head and Thai.
I also get bored very easily so love to learn new things and keep the grey matter ticking over.
Plus, which is a biggie in my opinion, is that by offering lots of things you are less likely to get RSI.