With all due respect, you'll need to decide what you want most: low cost, or convenience -- you seldom get both if you are insisting on an itinerary that is an unusual one for a tourist.
PL does not allow pickup at MCO and dropoff in Lake Buena Vista on bid wins, but Hotwire does. As a test, I just checked a 3 day rental starting on June 6th with a pickup at MCO and a dropoff in Lake Buena Vista, and I found a rate of $36/day on a standard. Lake Buena Vista is going to mean the general vicinity of WDW, possibly including the hotels out on Apopka-Vineland Rd. or on Irlo Bronson in the Maingate area, but it most commonly means the hotels on Hotel Plaza Blvd. near Downtown Disney. What that might mean cost/convenience wise is a $10 cab ride back to your hotel if you don't want to do some walking after your return the car. (It is possible to get the S/D rental desk, in which case you can just hop a WDW internal bus back "home" after dropping it off, but that's the luck of the draw -- you don't get to specify.)
PL bidding is likely to give you a much better price than that out of MCO; perhaps as low as $16/day plus taxes. The trade-off is that you have take the car back to MCO to return it and then take either ME or a Mears bus back to the resort. Mears will set you back about $20 for one person one-way. (Of course, PL bidding might also give you a daily price even lower than that if you choose to keep the car for your entire stay. Sometimes that is the best deal of all.)