Difference between blender h.264 and quicktimes'?

I’m curious why a 3 minute video I animate in blender outputs a lossless h.264 video that’s a 2.2gig .avi but once quicktime converts it and resaves it as it’s own 200 meg h.264 that is brighter. What am I doing wrong so I don’t get such degradation in quality and can still maintain a non redonkulous file size? Have blender animate to a different filetype? What’s the difference between the 2 h.264 codecs? Thanks!