The price on ARs may see a nice future decline, but because it is a constant target of gun control, I don't think anything with its future availability is ever certain. So, if it were me personally, I would purchase a lower or two (maybe one serialized for multical and one incomplete) and then purchase the 1911, allowing me to complete the AR at my own leisure, even if more gun control bills with bias towards black guns appear. If AR parts continue to fall, doing your own build might give you something for less money that best matches your preferences (for example, something with a trigger that is nicer than a basic milspec.) I like the Colt 6920 and think it is a very fine product, but IMHO the price premium paid might be most justifiable for someone holding on to it with intention not to use it as a longer term investment. Further, if the Hearing Protection act were to pass, AR component pricing might fall a ton, and there could be greater incentive to consider .300 blackout (or even 9mm) over 5.56, and this way you have left the door open for that option.
If you don't need another carry gun, and the 1911 will be mainly a target shooter with possible occasional carry, my vote is for the full sized. I am a huge fan of the Smith E-Series, which new is a little north of the budget, but used is well within the price range. I like it because of the fit and finish & quality of the machining, a great factory trigger, and outstanding endurance that I have seen first hand. I would highly recommend shooting one if you are near a range with rentals to compare the trigger and overall experience to other options.
If you don't need another carry gun, and the 1911 will be mainly a target shooter with possible occasional carry, my vote is for the full sized. I am a huge fan of the Smith E-Series, which new is a little north of the budget, but used is well within the price range. I like it because of the fit and finish & quality of the machining, a great factory trigger, and outstanding endurance that I have seen first hand. I would highly recommend shooting one if you are near a range with rentals to compare the trigger and overall experience to other options.