I was taught to have it on for start.
Looking at the Archer II POH it states that when the master switch is indicated, this refers to both Master and Alt switch and as such they should be depressed simultaneously.
Recently however a long way from home, I attempted a start and was suprised when the starter was not quite able to turn the engine over with the available power.
I tried turning the alternator off and it turned over and started. So I'm convinced the ALT load can make a reasonable difference to your start.