You guys always make me laugh when guys like you make such calculations and assume it's the absolute truth.
Not that there is no truth to it, but anyways... If there is something I learned in my gaming days is that you never have 100% of the informations available to you in a game. For example, the fact that you win some extra accuracy if you kneel or lose some accuracy if you carry something in your offhand while holding a two hand weapon is extremely badly documented, if at all. Things like that throw calculation off most of the time.
I am certainly not dissing your way of playing, but it's certainly not the one I'd use. The Laser Vs Plasma argument, for example, been up since almost the first day UFO was released and is still raging on to this date....
By the way, did you know that most big aliens are particularly resistant to explosions? The only way to really hurt them with a grenade is to aim exactly where they are so the full blast hit them...