I recently purchased a SureFire M500 forend/light for my RRA Carbine. I really like the light set-up but I have noticed that more people are either mounting a M900 or using a VFG and a light mounted on the left or right side. My question is is there a problem with the M500? What is the advantage of the M900 or some other light with a VFG other than having a VFG if any?

I have used both a M900 and a M500 (got my M500 from Grant, Highly recommend making the purchase through him)

The M900 VG is nice for long patrols, the vertical grip is just a more natural feel. The VG also helps for getting back on target after shots. However, as Grant stated, it can bust and you are out. That and It makes benchrest shooting difficult.

The M500 is nice because it keeps everything in a nice neat streamline package (thats cheaper). Within that package can cause more than normal heat buildup under the handguards, I have only noticed this on Full Auto Dumps though. The M500 also limits your space for rail accessories (Lasers, Bipods, etc).

I went with the M500A because I do a lot of prone position firing and the VG would just get in the way.