I would get a membership at both and hold on to both. AGC, IMO, has a very limited future. The Traps range might survive, but metallic cartridge shooting out there will eventually go the way of the dodo. It's being taken over by city expansion, and eventually they will lose the battle to keep it open.
Rondog, this is similar to BLGC, but this range lay out is better IMO. That being said, I also agree with Kelly. I've heard a lot about this range over the last 5 years and still have yet to see significant action towards getting the range built.
BLGC is closer to me, so I probably won't ever pursue a membership at this range. If I was in the Denver Metro area, I would. Even if you get a low rate membership, and the range dies you are not out very much money. If you get a membership now and Aurora dies it's eventual death, you may have very well saved yourself a 10+ year wait for a membership to the nearest range. There will be stampede to this range at the first signs of AGC's eventual downfall. The next nearest range of any substance is in Dumont, and they have a waiting list. Your choice is to roll the dice or take a small financial investment risk.
I am all for this range making it, and I hope they stick with the forecasted range lay out. It looks like a kick ass layout, expecially for us USPSA shooters. The one thing I would recommend to them is to cut one or two of the small berms out of the picture and add the space to the rest of the berms, making them wider.
Lastly, may none of the current AGC board members NEVER get any control in this new range. They are ignorant to any form of advanced firearms shooting, and would rather cower in a corner and cater to trap shooters than support the only shooting bringing in money (and influential shooters) to their current club.