I recently purchased an X300 with intentions of putting it on my LMT.  I ended up putting it on my Glock 17 and really like it.  I am now contemplating purchasing another X300 for my AR.  I have been doing some research and found the Surefire M600 Scout.  I like the Larue Tactical  offset "danger close" type mount for the Scout.  

Are there any obvious reasons to choose one of these over the other. (Scout M600 vs X300)???

I would be curious to see the following comparison:

battery life
throw/beam pattern
price

You could run the X300 at 12:00 if you have free float rails and that would be pretty nice...

I agree that putting the X300 at 12:00 would be nice, however I am questioning if I would have a clean sight pic with my Troy BUIS.    Also, I would have to move my front sight rearward and change the distance between front and rear sights from 14" to 11".  This would surely be ok, but I have always felt that accuracy is compromised as front and rear sight distance decreases.  

In fact, this is one reason I was contemplating the Scout with the larue offset close in mount.  The beam would be at 10:30 position, and the light would be somewhat protected in that position (moreso than at 9:00.  In addition, I would be able to keep my front sight at the end of my pic rail.

The X300 with the stock mount will not interfere with your iron sight picture. Sight radius, IMHO, is not an issue because they are backup iron sights. The M600C is slightly brighter than the X300.

I agree that sight radius is a non-issue due to the fact that you're not very likely to use them (unless you do not have an optic).