You have the advantage if you're better than they are.
They have the advantage if friendly fire is off.
More seriously though, I'm no master of doubles, but I'll give a go at breaking down the match somewhat. The big problem with dual falco teams seems to be that they tend to trip each other up -- SHL needs some degree of space, which is of course more limited in a 2v2. So either they don't approach much with SHL or they run the risk of stepping on eachother's feet and eating a tipper in the confusion (note -- I'm speaking generally; if they're really good they may have worked on ways around this)
So you have to take advantage of this. Pick smallish stages, work on leading the falcos into each other with your partner. Also note that falcos tend to rely on medium-long combos that your partner can disrupt, while marth is capable of pulling KOs out of the blue. Take advantage of this too. It seems to me that it is in team falco's best interest to turn the match into two simultaneous 1v1s assuming you let them do so. Do not let them. If you make them fight in tight quarters, you take away both their approach and their combos.