I would imagine print is faster on this instance because it doesn't have to wait for the file to be free for writing unlike syswrite. I would've imagined the size difference to be about half though, not that much.

My logging style usually depends on the program I'm working on. If I'm not sure the file isn't being written to from somewhere else (i.e. in multi-threaded applications), I usually use syswrite. For simple single-threaded applications I usually use print because IMO it looks cleaner.