I'm not sure that's actually the right question to ask. There isn't a better or worse system and in fact you sometimes need to choose, based on the issues that the individual has (system requirements and visual issues). The important think is to get a proper evaluation and let the person has to use the system for a few sessions to see if it really suits them. So your most imprtant piece of advice, I would suggest, is to buy from  a good supplier who is technology agnostic; will provide decent evaluations/loans; and who offers good support.

cheers

Jeremy