[sc_rufctr]

I've owned both and my 78SC is still with me. (I had a Carrera 2 that was sold during my divorce)

To me... Condition above all else matter the most. A good 915 is a joy to use but it doesn't suffer fools.
The G50 is heavier and don't even ask what they cost to rebuild. 915 parts seem cheap in comparison.

But a good G50 is robust and shifts like a Honda. Beautiful and precise. It really is hard to get it wrong.

So the choice is up to you but CONDITION is everything. IMO You're better off spending twice the money and a good car. Leave the "passed around" ones for someone else.