Actually, on BearShare I see a fairly representative mix of sources. That is,
slightly more LimeWire than BearShare sources, followed by Shareaza and
peppered with the rest.

Between BearShare and Limewire The difference is mostly that the odds are a
bit under one hop lower (out of roughly 3.5 hops on average) that rare files on
exclusively one type of servent's leaf nodes can be found in a single
search by the other type. Not a big factor until it's a file you want.

With rare files BearShare has a strong advantage because it can also search
by hash. It's larger query routing tables also cut waste traffic to a fraction of
what comes through LimeWire's 64 KB.

Knowing this, you can cover the odds by searching more often and starting up
a copy of the other one. Put it into ultrapeer mode, connect to the one
already running and search with both. Your odds of downloading go up.

When you're not actually there, let it continue sharing in the background.
Your odds of sharing go up.

Stay permanently on line like that and your odds start looking pretty good.