— I agree with what you are saying, but have you actually tried running random() and choose() a million times and comparing them? I have tried it just now on my very low-end android phone (which probably costs about $20 now).
1,000,000 calculations of round(random(17)) take about 5 seconds.
1,000,000 calculations of choose(1,2,3...,17) take about 6 seconds.
I really doubt that igalencar needs to spawn one million explosions at once, and even if he was, the difference in performance of these two math functions would be the least of his worries.