We have yet another first post on arfcom attracted by the NV forum; welcome to arfcom ShotgunWilly!
I have posted before that I am not a big fan of the D2 somewhat because of the size and weight and price, but most importantly the relatively low runtime of the illuminator and the fact that it shares the same battery as the aiming lasers. I do not own one, and seriously doubt that I ever will, but I have demo'd them on multiple occasions. Maybe they work great for some folks' applications; mine are just not one of them.
My preferred Class 1 aiming laser is the ITAL (or OTAL)..... compact, relatively lightweight, stupid simple controls, good QD mount, and cost effective. I don't use VIS lasers, but if you do, the CQBL is a good option for a little more $$$, and has slaved lasers versus the I2, but no QD.
As far as illuminators, I have M1-IRs, Vampires, and a TorchPro. They are different tools for different tasks, basically depending on range, and it would be an apples-to-oranges-to-limes comparison.
Just out of curiosity, what attracts you to the 720? I have never used one, but it seems fairly heavy at 9.6 oz., the controls look fairly complicated for ops in the dark by muscle memory, and they are fairly pricey. I also can't stand the SF QD mounts on any device...unnecessarily complicated.
Speaking of weights, since you indicate that as one of your selection criteria:
My favorite M600V with clickie tailcap and LT-172 mount is 6.65 oz.
My ITAL is 6.27 oz. with pressure switch.
The TorchPro is advertised at 9.5 oz., and I can confirm that mine is 9.54 oz.
The D2 is advertised at 12.5 oz.
The CQBL is advertised at 6.0 oz., which surprises me a little, but isn't unreasonable considering that it doesn't have a QD mount like my ITAL.
Think about this....for the price of a D2, you could buy a CQBL AND a TorchPro AND an M600V (shopping the EE for parts), and still probably have enough $$$ left over to buy an M1-IR, which many folks consider a "must have" in the NV toolbox. If you were to go the ITAL/OTAL route instead of the CQBL, you would most definitely have the $$$ for the M1-IR, as well as a nice dinner out with your significant other on top of that.
Your option 2 seems a much better way to go.