I am new to this game and would like some advice. I live in Seattle, which has significant hills, and lots of rain. I weigh about 210, and am an avid human-powered cyclist. I don't mind pedaling, but my goal is to replace some 10-15 mile cargo-hauling errand trips for which I currently use my car - e.g. the awkward 4 bags of groceries and a can of paint. My criteria are a range of 15 miles with an average speed of 10 mph with a bike trailer.
I've been looking at the various options for converting a std bike to partial battery power, and the options seem to fall into two camps: internal hub motors (e.g. Crystalyte) and "crank drives" (e.g. Cyclone). Based on the info I can find, there doesn't seem to be a significant difference in performance - seems like I can spend maybe $500-700 for either a setup like a 48V Crystalyte RoadRunner or a Cyclone 500W kit, and get approximately the same performance.
The main advantages / disadvantages of each I can see are that the internal hub gives more protection for motor to everpresent spray of wet oily road grit on winter Seattle streets, but involves the whole rear wheel and so if the rim gets wiped out there's more work to getting the bike back up and running. Converse for crank drive.
What am I missing?