What's the difference between Ultracel or Exilis Ultra in terms of results, discomfort & adverse effects?

I had a course of Exilis Ultra 360 (not Exilis Elite) facial treatments around 4 years ago and am considering it again, but there is also ULTRAcel available now. As far as I can tell both use both radiofrequency and ultrasound, so what is the difference? In terms of results, number of treatments (why less for Ultracel?), discomfort and possible adverse effects? Thank you