So my dilemma is to get one of the following:
www.supplycaptain.com/store/index.cfm?fuseaction=product.display&Product_ID=134
www.supplycaptain.com/store/index.cfm?fuseaction=product.display&Product_ID=82
or www.optactical.com/tagmotrm1mag.html

I like the idea of having shingles because I can add on pouches over it and use TT retention cords. Then there's the debate of either buttons or velcro for holding them in for the default retention.

I like the TAG pouch because it's simple, costs a lot less than the others (I would purchase two of the shingles) but no webbing on the front for retention cords or for adding other pouches.

I need someone to point me in the right direction. TIA!

What about this? www.optactical.com/tagmoshx6.html
TAG produces by far superior products as opposed to SDS or AITES, which is what supply captain sells.

I have one of those TAG shingles arriving in the mail in the next few days. If you want, I can give you a mini-review when I get it.

Went onto Diamondbacktactical and found this: www.diamondbacktactical.com/BattleLab-M4-Tiered-Double-Mag-Pouch-Holds-2-P704C111.aspx
Looks like a winner?

Look good to me.

DBT pouches do a really good job of mag retention: almost too good.  I've heard of some guys who were having trouble getting mags out quickly

The AITES pouches are better than the SDS ones in terms of construction and quality.  The AITES pouch flaps are adjustable for length as well.

Velcro is better than snaps simply because when snaps break (and they do), can you replace the snap yourself?  Probably not.  Velcro, on the other hand, can be replaced by the user.

The Tactical Tailor ones that have the shock cord are, in my opinion, a superior design compared to Velcro retained flaps.