Im ordering a new VCOG and can't decide which AUG to purchase for it to ride on, the A3 or the new M1.

The A3 has the slightly longer rail but going forward aftermarket items will be geared towards the M1s new receiver.

The M1s 'long' rail option appears as if will work fine and may be a bit lower than the M1s.

Spending money is fun but can still be frustrating....any thoughts?

The VCOG (I won't ask *why* a VCOG, overpriced in my book) uses an integral mount which is pretty short.
Unless you *need* extra forward rail space, I'd be all over an A3 M1 with the short rail.  

Yea I really don't need/want that much space which is why Im leaning to the M1, along with 'future' aftermarket potential.
As for *why* the VCOG...I tried it on someone else's set up and liked it.
Ive yet to find a 1-6x with a dedicated BDC/ranging reticle, batt illuminated RD, all FFP, and as low/rugged as the Trij.
The only thing close is the SpecterDR which I love & already have on another rifle, just want to try something different I guess.
If I end up not digging it after a while I can always just get another DR.

I'm with ya.  I was very interested when the VCOG was announced, but then saw the pricing and the BigJim review (check arfcom optic's long-ass review thread or snipershide), just not the right performance/$/gut feeling for me.
You might want to check out some of the new Burris XTR models - I *think* they can also be had in FFP.

Another option if you get a 'deal' on an A3 is to pick up a 2020 short rail + some quality rings, or the Manticore Talon (if they still have any, but I think they do).  The Talon precludes the choice of later deciding 'I want to go back to a red dot' (or Spectre DR), but either of those options will drop the weight and 'trim extra rail space' nicely.

Here's my latest configuration, with the Talon, Leupold VX6 1-6x (Pete's A2-ish rail is above it for rough comparison, with SP rings)

Here's a pic of the 2020 rail w/optic:

Info thread on the 2020: http://bullpupforum.com/index.php?topic=6740.0

The M1 with the short rail should be a nice fit.