This is an interesting topic. Here are the fuel canisters I think you are talking about:

https://adventuresinstoving.blogspot.com/2012/02/hank-roberts-stove-with-proper-canister.html

I thought you were talking about this kind of canister:

https://www.amazon.com/Gasone-Butane-Fuel-Canister-4pack/dp/B000JORB2M

which are still readily available and cheap. The first canister holds 6 oz of fuel and the second holds 8 oz of fuel so they have plenty of BTUs to cook. If anything they have way too much fuel for a weekend trip. I was hoping to find empty weights for the canisters but I haven't found anything yet. I feel like if Hikin Jim didn't then someone on bpl would have done this.

I thought I read somewhere once that these butane canisters are lighter per the amount of fuel they hold. That makes sense because, as noted above, they don't need to withstand as high of pressures.
They don't use them for backpacking because they don't work as low of temperatures as the mixed tanks.

You can get adapters to work with the standard iso butane canister stoves but they are dangerous: https://adventuresinstoving.blogspot.com/2012/01/butane-adapter-warning.html