Greetings,
Because I have also a license for another type of work, I am able to utilize PT equip. However, in my massage practice, I do not.
Personally, I have found that clients who want the "extra" therapies become wanting of them instead of hands on massage work, which I find to be better overall for many situations. What I am trying to say, is you can end up with clients wanting to "quick fix" and then when it does not "fix" them, they become somewhat frustrated. Sure on occasion a person may need a little extra help or a "boost", but I find that manual therapy does such a good job, that I don't use "quick fix", except on myself when I can't get to see another therapist.
That said, there are of course benefits to interferrential, US and EMS. They can get into and loosen tissues in a different way than our fingers, hands and self energy. They can ease some of your time worries: by possibly putting a client on EMS while doing something in another room, but checking on the client frequently --- or using the mechanical device to save your hands from extra work.
But, I just generally find it to be more of a hassle than anything else.