Late to the party, glad you went with white. Your concerns about it being too bright is easily solved by using fewer lights which = savings $$$.
And if you would have priced non-warranty interior liner panel.....its the same bright white.....I bet cost would have been similar to that of the galvanized. When I just did my shop last year, the exterior painted stuff was $1.85 per LF, galvanized was $1.49/LF as was the interior liner panel. And the place I bought also had what they called "rainbow" interior liner for $1.19. Rainbow was metal that was supposed to be painted white, but color didnt match perfectly. IE: could be a little off white or have a slight grey tint to it. Just something that didnt meet the standards of the $1.49/ft stuff.