Quality wise, I have never noticed a difference. I'm not sure theres any quality difference anyways, but there are some other advantages to bare wire besides convenience. Stray wires are always a danger and if a stray wire touches something that it shouldn't when using bare wire you may blow up a speaker, destroy an amp, or something else bad.
This is all worst case scenario and if you're careful the likelihood of this happening is low, but combine convenience with safety and you have more than enough reason for me to go with bananas. I use the Sewell silverback banana connectors, I think they're great and you don't have to worry about the wire pulling out (unless you really are yanking on it).
So wire safety is the biggest reason to use connectors, to keep everything from shorting, arcing, or other scary stuff.