I've been meaning to post on this thread for a few days now since I like to point out the differences in things.
To me, ENTPs are easier to spot than ESTPs. ESTPs kind of hide and do their own thing, which is weird considering they're written into the 'doer' stereotype who has all these friends and is reckless to the point they'd think killing themselves is fun.
ENTPs are very rough. In like, an oddly gentle way. The Ne makes them heavy and have this dewy appearance. Ne eyes have this certain wonder to them that is very cynical, yet at the same time certain. If you get a vibe like you're being analyzed by one of those giant computers from the 1950s, you probably just met an ENTP, bro. Ne is like a net casting outward, and once it finds its intended target, it pounces with whatever function is helping it. In this case, Ti helps it pin down ideas and search through the net. You could also think of a guy trying to harpoon a whale. Ti the harpoon, the ocean Ne.
ESTPs, on the other hand, are more abstract. You might find this weird though considering sensors don't get stereotyped this way, or have functions that would suggest otherwise. Se is a very hard to define function, despite it seeming rather straightforward. It is rougher than Ne in that instead of a net/sonar system being cast out into the open, it is more like an xray system siphoning through everything it sees and picking up on what's relevant to the person. TiSe works differently than Ne+Ti - whereas in an ENTP an idea can get pinned down quite quickly through Ti and be used by the user to navigate the situation, Se-Ti forces the user to jump on a moving target. It actually makes changes to the environment since it is acting on a very real possibility, which Se is known to locate easily. It's like shooting a gun into glass. Once you do it, it can't be undone. If you shoot a gun through a blanket (Ne), maybe you could sew it back together, idk *shrug shrug*
Since I can't find pictures to illustrate what I'd said, I'll use words.
Se - Ti - Fe - Ni: Backwards from the inferior function, you've basically got a gun ready to be fired. Ni is the bullet, Fe the cock, Ti the aim (or sights), and Se the trigger.
Ne - Ti - Fe - Si: Same here, you've got a type of gun to fire. Except this is a gun more likely out of the movie Ghostbusters, than let's say, Training Day or some other cop movie, eh? Si is the bullet (albeit a quiet bullet, almost as if the gun was operating on a silencer), Fe is the aim (sights), Ti the cock, and Ne the gunpowder. Both types are quite similar, it's just their functions interact differently from the other. Fe in an ENTP is more of a means to the end type F function, because it supports Ti directly in getting a goal it wants. Fe in a ESTP, though, is a bit more like an afterthought which pillows any mistake the ESTP made in going after a goal with Ti. It softens. An ENTP's Fe burns, turns, and twists, and has a more clear Fe flavor to it.
Most of the people in this thread aren't far off, though - especially evilrubberduckie and theforsaken ^^;