I would go for plastic, and pick a size relative to what you are filling. filling a truck from a 5 gal is doable, but filling a chainsaw is painful. 2.5 is a good medium, with some 1gal for little equipment. I prefer the vented ones, as the ventless ones never really worked for me. if you stick to the same brand you'll get a better fit for spouts. bendy spouts are the most common(the best are the kind that hold a bend), but the valved ones work well too. I used a jerrycan hand pump thing at one place I worked "eze-pump" or some such. it was a pain for pumping uphill, but for filling the boats it worked to start a syphon from the can to the boat tank, then you could easily pour the last third of the can.
Unless you are going to be hauling fuel a lot, I wouldn't bother with the NATO ones. The normal home consumer ones are fine, I've used lots of the sceptor brand ones and they seem to seal well, and are very tough. Also, it helps to designate cans for clean and mixed fuel, just prevents any problems, and on buggy days, just run the old mixed fuel in the mower for a little extra anti-bug pollution!
Fuel longevity is based on oxidation, so better sealed gas lasts longer. However you should still be rotating the fuel every six months or so, I consider the stabilizer to be cheap insurance.
If you can't find something you like at your local hardware store, try a chainsaw or ATV dealer, they might have better stuff.