They're all horrid to step on, so that's not really worth discussing.

The US plug (NEMA 1-15P is the 2-prong version, or 5-15P for the most common 3-prong grounded) is actually pretty decent. They stay in sockets pretty well if the sockets aren't bottom-of-the-barrel garbage products which, sadly, many things in the US are in general.

What many people miss when comparing US and EU plugs are that they're actually doing fairly different jobs. The 120V mains in the US is significantly less trouble than the 240V in Europe, so you can get away with a lot less mechanically on the plug. The US NEMA 6-15P plug design (the 240V version of the standard plug) is, accordingly, kind of shit. But at least it's rare enough that receptacles tend to be of decent quality, which mitigates a lot. The locking versions (L5-15R etc) are actually quite good, and should almost always be used when possible and appropriate. They're good to 480V and even a bit beyond -- not just working but actually good -- and you can't say that about most EU plug designs. You guys have those horribly bulky pin-and-sleeve disasters and we get nice NEMA locking plugs for our three-phase.

One of the other things that European plugs have to deal with, and US plugs don't, is that European electricians have no idea how to separate hot and neutral wires and basically wire them up randomly. This has major consequences in a lot of product design and is really really annoying when you're trying to build something safe. (Namely: in the US you're often (but not always) not allowed to fuse neutral wires. That makes sense, for safety reasons. You have to fuse hot... but in Europe you don't know which one is hot, so you have to fuse them both. Which means you just fused neutral. Design conflict!) That shows up in the plugs, too; with no idea where hot is, you have to be more careful and can't use neutral to help you out.

British plugs are worse to step on, not because the pins are any worse to have jammed into your foot but because the design of the plugs means that if you leave one unplugged on the floor there's an excellent chance that it ends up in caltrop configuration with the pins pointing upward, whereas a US-style plug is (I think) more likely to end up with the pins pointing sideways where they're less likely to hurt your foot when you step on the plug.

But in all other respects the British mains plug design is really rather good. It does a good job of making partially-plugged-in plugs still safe, it's nice and robust, it readily stays firmly plugged in, etc.; US plugs are much worse in these respects and I think so are typical continental European ones.

BS 1363 isn't an EU plug though. Doesn't have issues with separation of hot and neutral wires (and does have a fuse for the hot wire built in) and nor is it specified with the idea that electrocution risk is no biggie or that not falling out of walls (a big issue with some Euro plug and socket combinations too) is up to the manufacturer. And having one type of plug for all regular home appliances in the UK and a different one for three phase feels like a more sensible split than the range of 2 and 3 pin options of varying quality and compatibility that CEE7 and NEMA present.