Unless your problem is "we solve epicycles" - neither is going to insulate you from obsolescence.
The benefit to targeting a "problem" is that you have a preexisting need. An "idea" with no existing "problem" may require several years of extra lead-in where you are struggling to get people to understand what you do and why it should matter to them. It can work, but the ratios are less favorable for a VC-style investment which looks for fast turnaround with minimal risk and orders-of-magnitude payoff.
The benefit to targeting a "problem" is that you have a preexisting need. An "idea" with no existing "problem" may require several years of extra lead-in where you are struggling to get people to understand what you do and why it should matter to them. It can work, but the ratios are less favorable for a VC-style investment which looks for fast turnaround with minimal risk and orders-of-magnitude payoff.