I do still have my die hard sugaring clients who say that it is less painful for them than waxing. However, as Mat has already said a lot is down to the therapist and how good they are with the "tools of the trade".
I trained with Nagwa as Sukar and if you want to go down the sugaring route would highly recommend her.
I have however tried Zhara sugar paste and I found this a little better to work with than Sukar.
I try now to do as little sugaring as possible due to an arm injury but why not offer both if you can afford to do both courses.
However, what I would maybe train in one, become competent at that and then add the other service at a later date.