Ok, here's my tuppence worth.
I drag a lot of wheelies about cos I'm a wheelie bin cleaner. Logistics are :
Weight of bin - about 22kg
Volume of bin - 0.33m3
Weight of bin full of water - 352kg (a third of a ton)
BUT it seems to me that you don't need to fill it full. Just a sixth would do to get 2 of those 25 litre barrels you all often talk about.
Main prob is in and out of the van. Most people can manage 25 litres at a go but 50 litres is a lot. Plus the weight of the bin. A barrel will weigh (I'm guessing) next to nothing when it's empty.
So it IS a good idea, which falls victim to it's own success through weight pulling logistics.
Hence in all honesty, and speaking as a bin cleaner who's never cleaned a window - go for barrels
- but ten out of ten for lateral thinking