Big Dan was bigger and stronger. Maybe with a much speed. Rozier arguably had a better offensive line and Gill and Fryer and Jeff Smith to get him rest. I'm a big fan of Rozier but I really liked what Alexander brought.
Alexander had "issues" with holding onto the ball to say the least. Rozier rarely fumbled and was tough as nails (Missouri 82 game). Dont forget he pushed Roger Craig to the backup role and eventually to FB (in the weak set).