Any advice on Mobile Mappers and Submetre GPS?

Evening All!
I was just wondering if anyone out there had any advice on a good, industry standard Mobile Mapper and Submetre GPS? Is there a make and/or model that is used commercially by a variety of units? I’m only just starting to research this so am a tad clueless at the moment, but I know I’m looking for something that is quite straight forward as it will be used for teaching purposes – but I also want to find something that will enable students to be prepared for using one in professional practice. Any advice welcome…!
Many thanks,
Hannah.