I was running through this same debate in my head a week or two back. I love the look of the 4C and the sound it makes. I have never owned an exotic like this so I was trying to convince myself that I should buy one now, whilst I am still flexible enough to get in and out (I'll be 59 this year).
So I spent an evening reading reviews and watching YouTube videos, particularly ones focusing on the practicality of living with one. And in the end I came to the conclusion that I'm better off with the V6 916 Spider.
I live very close to a very uneven level crossing. I ground the Spider if I'm not careful. I am pretty certain the 4C would ground every time. Or get stuck
I also have to cross a narrow bridge on my way out, with just enough room for two normal cars to pass. Not a problem with the Spider but the 4C is allegedly wider than a Range Rover! The same applies to my garage - I can park next to my wife's car and have room to open the door and get out. The 4C would be an issue.
The 4C is just not practical. My wife and I went out the other day. We chucked the coats, bags etc. on the parcel shelf, enjoyed the roomy cabin, and on the way back had a boot full of purchases. This just isn't possible in the 4C - no interior storage (no glove box!) and tiny boot.
Now I have changed the springs and shocks the Spider is a very comfortable car for a long drive. Admittedly I haven't driven the 4C but reports suggest it is definitely a sporty ride, not a grand tourer.
I love the sound and responsiveness of the V6
As others have commented, I wouldn't be happy spending that much money to then have to spend more getting it sorted. Tramlining should not be a problem in a modern sports car.
So I have convinced myself that I should stick with the 916. And, having saved £40k by not buying a 4C, man-maths says I now have this to spend on improving the 916 or buying other toys