@Funcha: That is something I have been wondering about myself lately. I know from experience that encodes with the top and bottom bars cropped always look better in terms of image quality than 1920x1080 encodes of the same bitrate but I appreciate that a lot of you like creating playable blu-ray discs that need the encode to be 1920x1080 for you not to have to reencode. If I start releasing 1920x1080 mkv releases on tehparadox though, i'll have everybody on top of me asking why i'm sacrificing image quality by not cropping the bars like all the other mkv releases do.
It really is a dilemna. I'm just glad that with my regraded IMAX releases like Interstellar and Guardians of the Galaxy I don't have to worry about it because those have to be encoded in 1920x1080. I wish that sony, microsoft and other manufacturers of blu-ray drives would get their act together and allow mkvs to be played natively off their players, it'd make everything so much simpler.
As a general rule, i've found doubling the bitrate pretty much maintains the image quality, so if you create bd-50 1920x1080 reencodes of my 22gb cropped mkv regrades, they should look pretty much the same in terms of image quality and they would be playable straight off the drive. That would be one solution.
Another solution of course would be me also creating 1920x1080 encodes of releases i've already done but that would take a great deal of time with the amount of regrades i've completed and I wouldn't know which releases to start with. Perhaps if I set up some sort of poll listing all my releases, then everybody could vote on which releases they'd want me to create 1920x1080 encodes of first? This sound like a good idea to anybody?