I was just amazed you were able to list so many potential good 'uns!
How would you rate the quality in the MLS vs the Championship? And what about the physical demands?
The yo-yo relegated clubs are a step above MLS, but after that the leagues are very comparable.
The unique salary cap and spending rules in MLS mean that there is is a greater disparity between the level of starters and the depth. At the top level, the attacking talent and a lot of higher level first choice starters in MLS, but the depth of rosters is much better in the Championship.
Overall, if a player is a penned-in starter for a MLS team, I would expect them, at minimum, to be a solid contributor to a non-top 6 Championship club.
The physical demands are less in some respects and greater in others. The on-field physicality is a bit higher in the Championship. A bit more rough and tumble league versus MLS which has a sizable central and south american influence. However, the travel and environments are much more physically demanding. We are a massive a country with 4 different time zones. Our summer-based schedule also means that our matches are often played at 30°C+, even at night in some cities. Players new to the country/league often talk about the physical toll that takes across the course of the season.