I feel like something missing in this perennial discussion is the question: why do we need this particular term at all?
There is no use for a phrase that means "option X is better than option Y under all circumstances." I'm not sure there's a use for that in real life; you can nearly always find an edge case.
I see two uses of this phrase commonly:
X is strictly better than Y, if you ignore cost.
X is strictly better than Y, if you ignore edge cases.
The first can be useful if all you're doing is comparing costs. All other things being equal, would you rather have a single Goons or a single Militia in your deck? Obviously a Goons; it has the same effects as Militia, plus other positive effects. Therefore, Goons must cost more than Militia. While I suspect this might be useful for Donald when creating cards, and can be useful for comparing power levels, it has little utility when playing the game. The only use I can imagine is something making a decision between, say, Village and Worker's Village when you have $4, or things like that.
In the second sense, this is a theoretically more powerful tool, but it effectively requires a definition of all the possible edge cases. So just... toss this out. It's a garbage phrase that is of no use except debating its use. It's like a sign that says "DO NOT TOUCH THIS SIGN." Like, why even put the sign there?
"X is usually better than Y" is just fine for discussing strategy. Perhaps even "almost always." Then you can include things like "unless" or "especially".
Warehouse is usually better than Cellar, unless you have a large hand.
Worker's Village is almost always better than Village unless you need unique cards or to end the game.
Count is almost always better than Mandarin unless you're using Mandarin's on-gain ability.
Heck, you could even expand on those opinions. It might require more writing or defending your position.
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As to the OP though: I tend to agree Boons range from basically nothing to really really good, depending on situation. The draw 2, discard 2 sucks if it causes a reshuffle (and the Cartographer one), and of course the gain a Silver can be actively harmful, but almost everything else is good. So yeah, Bard is almost always better than a hypothetical terminal Silver with no bonus. Is it better than other terminal Silvers? You'll have a harder time convincing me of that.