[TSM330i]

I technically have three manual cars (991.2 C2, 2015 GTI and Z4 racecar).

I do not like driving an automatic at all, much less so a sports car with a flappy paddle gearbox. It takes a lot of the fun away for me.

Your question: Should you buy a 2012 V10 R8 with a manual, even though it costs the same as a 2017/18 R8?
The easy answer for this is yes! There is a reason why the manual car is getting a premium. It always will because they simply cannot be had anymore.
Your 2017/18 will not be unique, except for the fact that it's an R8. When you look to move on from the car, there will be plenty of '17 or '18's available to compete with yours.
Now, the 2012 with the manual transmission will be a whole other story.

Plus, the driver involvement of the manual V10 R8 will be intoxicating. It will be full-on driver immersion in fun.

It's a win-win as far as I'm concerned. Go for the manual car. You won't regret it. The 2012 is a really stoudt car and will last a long time. They got a lot of the bugs out of the cars by that time.