I think the USHobbies stuff was just a smidge nicer than the Max Grey/Gray. Generally the USH stuff had cast gear boxes and slightly better motors. Also they used more lost was castings where MG stuff had turnings. Other than that the construction was about the same quality. Probably there is a blur between them and my opinion is based on having models on both sides of the transition but not real close to it.
Max Gray or his estate sold the business to Levon Kemolyan (SP) who already had Kemtron I believe. He renamed it US Hobbies. Both companies as far as I know had exclusive contracts with a Japanese builder, called KTM, hence the models are very much alike. MG may have used some other builders too. I have never seen a USH model without the KTM plate underneath.
