I've been using the Euro surplus metal cans since the early 90's.

When you get them, hopefully NEW, buy some spray undercoating for cars and hit the bottom of the can and the seams heavily. Ideally the whole can, but if your short on undercoating the bottom is the point where I've seen the most failures in 30 years.

Try to store diesel in them first if you have the option. When I get new ones I pick up some fresh off road diesel for my heavy equipment in them and fill the backhoe, bulldozer and excavator up. Diesel being a lubricant. Don't know how much this "really" helps but I've tried to do it every time.

The seals on the mouths will tend to go bad over time, but not in large quantity. We usually have about 20 cans in rotation and usually only 1 or so has a leak that you will only notice if you put the can on it's side instead of straight up.

Remember the cans will use special nozzles, and there is both a wide mouth and a smaller sized version. Get at least 2 nozzles if you have say 5 cans. They don't seem to be a perfect fit on every can, so being able to change one out to find the right fit is nice.

You WILL over time, start to find small bits of rust in your fuel-  again I'm not talking about six months or maybe even a few years- this is from the cans. About 2 years ago I had a rash of fuel issues on a tractor, a bulldozer and a backhoe. I changed fuel filters, purged lines, etc. Had to have a couple of fuel injectors rebuilt. Guy said "do you fill from cans or from a tank?" When I said cans he frowned and showed me some of the gunk that had accumulated.

Sometimes also you will see bits of whatever the red'ish coating inside the cans float while filling. Last fill up on off road under pressure at a station I watched what seemed like a big paint chip float around while the can was filling. I tried to float it out while filling but it didn't work. I marked the can and was sure to use a filter funnel on that one- never saw the piece come out.

I sometimes use one of those funnels with a screen, but not always. Those would be crucial to have post SHTF as you may be forced to use really old fuel and/or barter for fuel that you haven't totally vetted.
After those incidents I added in line disposable fuel filters also to the equipment and put about 20 in storage along with a roll of rubber fuel line and some hose clamps for repairs. This was all heavy equipment and tractors.  These things plus some starting fluid would be handy to keep as extras.

That's essentially the product I was talking about- has a filter inside the funnel.

The larger one you listed would be excellent for heavy equipment, thanks.