[chimera]

We already know we can operate successfully using solar power on Mars; why not use what works and is cheap?

Cheaper doesn't always mean better. You'd be better to maximize the (scientific) return on your dollar invested by spending a little more to assure reliability and enhance capabilities (i.e., being able to go where you couldn't otherwise go, like polar regions and/or canyons and deeper craters, where there may be evidence of water).

[Yossarian]

You'd be better to (...) enhance capabilities (i.e., being able to go where you couldn't otherwise go, like polar regions and/or canyons and deeper craters, where there may be evidence of water).

See my post #14 above for why mission planners want to keep a nuclear powered rover from going near water.