A nice feature of the Vang side saddle, is you can easily switch from brass up to down, just by flipping the shells/velcro. Since brass up is more secure, but brass down loads faster, it is nice to be able to quickly change orientation. I use vertical orientation to separate types of ammo -- typically I run my Brenneke slugs one way, and my rubber slug (for non-lethal discouragement to a bear) the other way.
For me, while I like the Magpul rear stock a lot, the jury is still out on the Magpul fore end. When shooting Brenneke slugs, the lip at the rear of the Magpul fore end can be painful.
With both the Magpul and G,G&G fore end, I have a Surefire Scout light with a pressure pad that I can attach and remove as conditions warrant.