As a mobile tech I offer the following:
L&P tip and overlay
L&P sculpting (with forms)
L&P natural nail overlay (goes with out saying)
L&P custom blend, (Sculpt/tip & overlay)
L&P glitter tips, embedding of flowers, flat stones, glitter fades etc.
Airbrushed nail art
Hand painted nail art.
Manicure
Hand treatments
Pedicure
As you can see I'm a L&P girl, the reason being is that I started my training with Creative with it, and feel extremely comfortable using it. My clients never ask for anything else, although they are aware of the alternatives.
When ever I get a new client it's not often that I get asked for anything other than L&P.
When I am able to do full time (eventually) I will consider doing Gel to add to my menu, as I would be dealing with a larger number of clients. Where as, as it stands, I would not benefit from investing in a new system at the moment.