I would like to suggest BitComet show the availability of a download item.
Availability is calculated by the percent of pieces that can be downloaded. If the availability is 1 or more, then it is calculated by the piece with the least amount of peers having it.
The fractional is calculated by the percent of pieces that have more peers than the piece with the least.
For example (for a file with 10 pieces):
One peer has only 8 pieces -> 0.8
Three peers have the same 5 pieces -> 0.5
Peer A has the first 5 pieces while Peer B has the last 5 -> 1.0
Peer A have the first 8 pieces, while Peer B have the last 8 -> 1.6 (as all 10 pieces can be downloaded, and 6/10 pieces are carried by both peers)