I'm taking it as a "beware sign" for knowing what's ahead; i.e. to consider the big-picture around whatever you are building (it's very easy to get sucked into some "interesting direction" and get side-tracked; us geeks tend to do that).
To answer your question: yes, if I would be an investor, I'd also want to see the prototype/MVP, because:
- less risk taken
- 1 picture == 1000 words => demo == millions words
- you show you can execute what you wish (not getting side-tracked)
from founder point of view because:
- early adopters will help you shape your product (I just pivoted this month)
I've never started a business so my naive viewpoint is that many of the most successful companies appear to be built on having a great product alone then focusing on profit second, for example Google, Facebook, and Twitter. These are the largest of the the large though, so is the story different for smaller companies?
In most cases "build great product first then focus on profit later" means you run out of money before anyone buys enough of your product for you to get back in the black.