Great question and point Kurt! Solar panel selection is usually not just about price per watt. For some it's about the technology, the brand, the efficiency per square foot (due to limited roof space), what else the company produces or stands for besides solar, warranty length, types of connectors or junction boxes on the back, etc.
To answer your question specifically, my suggestion would be to consider solar panels which use amorphous or thinfilm technologies. This type of PV tends to produce more power in diffuse light conditions (i.e. overcast, dawn or dusk) than polycrystalline or monocrystalline. In fact, generally speaking, an amorphous or thin film solar panel would produce more energy (watt-hours) over the course of a day than a mono or poly crystalline panel of exactly the same wattage rating. This effect is because of the fact that they are able to capture more power from low light and indirect light conditions.
Efficiency is often too focused on as well as the most important thing. It's only important if you have limited space to place the panels or for some reason the weight, the larger dimensions cause problems in the install or transport.
Some examples of manufacturers that produces amorphous and thin film solar panels are:
Global Solar
http://store.altenergystore.com/Global-Solar/m30/Kaneka
http://store.altenergystore.com/Kaneka/m37/Uni-Solar
http://store.altenergystore.com/Unisolar/m79/Iowa Thin Film (Power Film)
http://store.altenergystore.com/Iowa-Thin-Film-Technologies/m35/As you'll see many of these companies produces PV that are flexible and foldable. However, Kaneka & Uni-Solar produce modules currently with rigid frames appropriate for mounting on a house.
Hope that helps!
