So how about this? They are both terribly inefficient unless the power generated doesn't have to travel more than a few hundred feet.
What would make Wind or Solar any different to send over transmission lines than anything else? Once it hits the transmission line, it's not like it looks any different, no matter the source it started from.
Also, they become less efficient if you can't use the power at the time it is generated and need to store it. It's not really an issue now in most places but there are conversion losses to store the energy and then bring it out of storage.
With nuclear (or fossil fuels) the fuel is the storage medium and you don't release the energy until you need to use it.
That's a start up and shutdown characteristic as power plants are managed to match usage. Nuclear isn't a great example here, as it's kind of a pain to ramp up and down and a huge pain to turn off and back on. Of course, when you exclude initial investment and only manage on the price per kilowatt produced to run, nuclear is so much cheaper than fossil fuels that utilities just run it all the time as base generation and ramp the others up and down instead.
It's kind of a bummer that hydro has a relatively easy ramp down and up characteristic, just flow less water, but that it's price to run per kilowatt is so low that it also tends to be part of base generation and run all the time too.
Wind and Solar have their own issues with ramping up and down, mostly that they're subject to outside conditions imposing that instead of only a management decision. It's why good wind installations are done in areas that basically always have wind.
The only reason we talk about storage in relation to Wind and Solar is to smooth out those outside disruptions and to provide power when there's no wind or sun. But, if you just keep something else in the mix instead of a "100% can only have wind and solar" solution, that other thing can act as the buffer instead of storage.
We need a mix of generation, with different parts having different characteristics. Each optimized for the value add that one brings. There is no single one best, but a best system outcome instead.
Just like there's no one best ride for providing capacity at the park. It needs a mix of omnimovers, thrill rides, shows, small, and large. Each brings it's own advantages and disadvantages. The mix creates something better than the parts.
PS: A jet engine powered by natural gas or jet fuel has amazing ramp up and down characteristics. It's bad at just about everything else, but still an important niche.
