That seems to be a bit of a false dichotomy, though. I'd assume it'd be vanishingly rare to find someone whose only motivation to work for a company is their illiquid equity comp.
I hear a lot of people who suggest that equity in a private company is worth $0, and I even preached that as well, but I think it's counterproductive to do so. Sure, it's difficult to properly value such equity, but I think discounting it down to $0 is nearly as bad as assuming it's worth a lot more than it's possible to be worth.
Let's say that you're lucky enough that comp isn't your #1 motivation for working at a company; maybe it's down at #4 or #5, after working on cool projects, autonomy, working with smart people, etc. Comp is important, but it's not the most important thing. If you're really convinced that a particular private company's options could be worth something someday, and you're able to negotiate a reasonable cash salary, looking at the equity comp as a differentiating factor as compared to another company that has a less attractive equity package is perfectly reasonable. Assuming that the equity packages of both companies is $0 throws away useful information.
I think of the "value it at $0" strategy as a knee-jerk reaction to overzealous fresh college grads thinking a big number of options automatically means they're going to be rich. It's a useful phrase to throw at someone who has limited ability to do a risk assessment, but is a bit patronizing to someone who does.