Call or write to Robbins and tell them you're betwixed between Robbins and Medallion. Let's see what they say. Then, bring up your 'concerns' about the differences in the floors and, again, see what they say.
The sheen issue could be from a number of causes. The KEY is to find out how many coats of finish polyurethane are applied. If it's an in-factory finish, at least 6. If you're going to get an on-site finish, at least 3.
I will say this about Medallions. Ask Robbins about the refinishing 'record' of that brand. And ask Medallion how may refinishes can be had out of their brand. For more help, visit WoodFloorsOnline.com and you'll drown in help.