Well I think practical and cheaper almost always go together and this is the case in this area as well IMO. Propane runs $3-$4 per gallon, you have to have a giant tank mounted either in the bed or under the truck some where, finding some place to fill it IS a PITA, propane raises EGTs, you inject it preturbo (which is an explosive hazard IMO), need I go on?? Water methanol on the other hand can be had for about $1-2 a gallon, tank is MUCH smaller, WM can be had at just about anywhere that sells windshield washer fluid or you can just run water, WM lowers EGTs, IMO this is the more logical choice. JMO and hope it helps.
You can run 25% alchol with the cheap blue windshield washer fluid, 50% boost juice, and/or make your own mixture if you buy racing alcohol.