It made a difference (in my unscientific tests). I haven't dug into it too much but the jsperfs that I could find show it being quite a bit slower:
http://jsperf.com/if-versus-math-max
http://jsperf.com/math-max-vs-comparison/3

There's still a lot more in this function that can be optimized, too - it's the slowest thing when drawing a lot of scopes.