Funny you mention this because I just this minute finished a test. I have Audio Technica ATH-M40fs studiophones and my brother has ATH-M50 monitor headphones. They just went head to head and I couldn't tell the difference. Both very high quality headphones. I note that his cost twice as much as mine but I recall paying much more than what they are going for now when I bought them two years ago. His have angled configuration since your ears are set at an angle but I've never had a problem with mine being uncomfortable.

Of course, most expert says we should mix with monitors but I've always used headphones.