(this will probably open up a whole shitstorm, but:)

Are there important functional differences between a "Clean Energy Standard" and a "Revenue-neutral Cap and Trade System"?

As far as I can tell, CES is a more popular way to frame C&T (though costs are more hidden).
(1/a few)

Like if a CES and C&T had the same scope (just electricity, let's say) and the same trajectory (20% reduction in 10 yrs, 50% in 20, 100% in 40), then they should produce approximately the same outcomes, no? In either case, you'd expect the system to search for lowest-cost solns.

The mechanism is different: in C&T, there is a tradable commodity, so price and exchange are explicit. Under a CES, you'd still expect "the market" to search out the cheapest ways to reduce emissions. Obviously, real-life behavior would shift both strategies away from "ideal".

Maybe the biggest difference is that a CES treats a MWh from an inefficient coal plant as equivalent to a MWh from a very efficient NG plant as the same thing, while C&T considers the first one to be quite a bit worse. CES has a focus on MWh and not emissions.

Unless I'm missing something, I think the differences between C&T and CES are:
1. CES is more popular & simple.
2. C&T has more transparent costs.
3. CES focuses on MWhs and not emissions.
4. Diff. between ideal and real-life behavior means that implementation will differ a bit.