That depends on the player. A fully informed choice of potential actions and outcomes may be available to a very experienced player but I dare say they'd be the minority; but I'm not sure that's even relevant, as every ability having much the same outcome doesn't really lend itself to either character or player progression IMHO.
Of course a lot of it is still dependent on specific effects and circumstances, but I still think that being over-zealous about equalising everything risks making choices and consequences rather dull. Although some players will abuse stand-out abilities to the point that they could almost be considered exploits, I'm left feeling that the cost of addressing that particular issue may be too high when looking at players in general.
Talking of over-equalising, I'm somewhat reminded of a current rant about the CD "loudness war" where the EQ of everything is ramped up to the point where all finesse, fidelity and interest is lost. That may or may not be a good analogy, but I couldn't help but think of it.
