Re-rolls and probability

I noticed this interesting post over at The D6 Generation yesterday. It's from a listener who writes about the probability of scoring a certain number on a D6 with and without a re-roll, so for example when firing a twin linked weapon. You can read the way the binominal probability works in the post, but I just wanted to share the most important part, the probability table:

2++ = 97%
3++ = 89%
2+ = 83%
4++ = 75%
3+ = 67%
5++ = 56%
4+ = 50%
5+ = 34%
6++ = 31%
6+ = 17%

+ = w/o a reroll
++ = with a reroll

Let's take an example. Say a Chaos Terminator with a twin linked bolter (rapid fire, twin linked) and a Space Marine Terminator with a storm bolter (Assault 2) are both firing at a target 10" away. Both are BS4, and both weapons are the same strength and AP.

Each shot from the Chaos Terminator has a 89% percent chance of hitting, and so has a 79% chance of hitting with both shots (0.89 x 0.89).

Each shot from the Loyalist Termaintor has a 67% chance of hitting, and so has a 44% chance of hitting with both shots.

So on pure stats, the twin linked bolter is better at this short range. Of course, at more than 12" the storm bolter would get an extra shot perhaps giving it the edge there. Being in terminator armour, the unit can still charge after firing it's bolters.