The Vanquish interior leaves a lot to be desired from a car of that caliber. I worked at Ford Motor Company at the time it was being developed and spent time in one of the development mules. While Ford did the best it could and took Aston forward, at the time, it simply didn't know how to create a true luxury car.
The dash buttons are inexpensive plastic and they creak when you press them. The key fob is from a Focus, which is a lame, black, functional, cheap looking fob. The car certainly has power and the exhaust bypass valves are incredible. I'm not saying it is all bad news, just that the Vantage is dead on perfect. Ford learned quickly how to create perfection and the Vanquish was part of the learning curve.
I'd say go with the Vantage, unless you really need the V12 engine.
The DB7s have certainly dropped in price. Aston's are good at doing that, and quickly too. I think the DB7 is a good looking bird. It loosely underpinned the styling on the DB9. Lot's of family resemblance.
I suspect the DB7 will be a car 20 years from now you will look back at and be proud to have owned (if you don't choose to keep it). Mr. Bristow, I say just do it my friend. You get a lot of car for your money and with that V12, lots of pleasure, pride and torque. Be sure to have a full pre-purchase inspection by the service station of your request! Cheers.