Why not both? Neither works right now, it's probably prudent to try as many interesting things as possible.
1. Solar roadways is a terrible idea that will never be a good idea. It is strictly worse than building a roof over the road and putting solar panels on that.
2. Roughly half the renewable energy on earth comes from decaying isotopes and half comes from sunlight. If humans want more than that, they'll basically need to get it from sunlight not hitting the earth i.e. solar power satellites. That is a road that we'll eventually go down, but not for quite some time.
Solar roads has the distinct advantage over covering all the roads in that it's not an eye sore and fits more seamlessly in the scenario we figure out the engineering.
There's this idea in economics called opportunity cost. The simple version is that if we fund bad ideas that can't possibly be good, we lose out on the good ideas we could have funded but didn't.
This is the reason you don't heat your house by burning paper money. You'd rather have rent and groceries and heat instead of really economically inefficient heat.