I have seen a lot of negative comments about the Flynn frame from users who found it bulky and difficult to use. A few people seem to master it and love it, though. Have seen lots of positive posts about the Ken Lund frame. If you search the QB for "Ken Lund" you should find several threads about it, including one that modifies the carriage so it works better.
I believe these are very different types of frame also. With the Flynn setup, you are moving the frame; with the Lund setup, you are moving the machine. There are lots of Youtube videos about the Ken Lund frame that you might want to watch. There may be some for the Flynn frame too.