I'm not sure the variety would help as much as folks think.
A preparing caster has lots of variety, yes. But putting that variety to use requires a plan and/or foreknowledge of what you're getting into. Once you know, you can set yourself up, but then you're fixed into that plan.
The bard, on the other hand, seems to me to be the sort who mixes in to a variety of different situations at the drop of a hat. That's not something you can prepare for. While the bard's list of known spells is small, within that list the bard has far more short-term flexibility than a preparing spellcaster.
Basically, the bard seems to me to be a master of improvising to meet his situation at the time, and preparing spellcasting doesn't fit that role. YMMV.