There is a lot of personality generalizations I could suggest of the many EHX Choruses. Here’s my quick opinions/characterizations, but trust your own opinions over mine. I’m primarily a bass player.

Small Clone – A famous anecdote is that the United States space program spent millions of dollars developing a pen that could be used to write upside-down while in space. The Russians used a pencil. The Small Clone is the Soviet pencil– a brilliantly simple tool. It’s a very lush, juicy chorus effect. It’s more juicy with the color-switch down, and more “intense” with it up. It does a great vibrato with the rate knob maxed out and the color knob down. For “over the top” settings, you can get a kind of underwater effect.

Stereo Polychorus – I think the Polychorus should have always remained the “Echo Flanger.” It’s a much better description of what the pedal does. It’s a very bright flange/chorus thats built around this echo, faux-reverb kind of sound. Unlike the Small Clone, the Polychorus can’t do lush, juicy chorus. It accels at a very bright, chiming, kind of chorus. It stands out in a mix. The Flanger setting is very good. It’s a pedal that does have a learning curve, the knobs are very interactive. You’ll be tired of the “sea-sick” swirling it does when you’re figuring out how to shape the effect, but it’s worth it to learn. The “echo” aspects of it are what make it so unique, and it does a pretty awesome reverb-imitation on certain settings. It’s an awesome pedal, I use it and love it, but you have to decide if you want a chorus that is for texture, noise, and ambiance or one that is simply used to color a guitar signal.

Stereo Electric Mistress – The biggest difference between this and the aforementioned pedals, is the Stereo Electric Mistress is a digital effect. It does sound very good, but analog-purists always chafe at how clean and crisp digital effects sound. Personally, its up to you. It cuts through a mix very nicely, sounds good with distortion. Being able to dial in the chorus along with the flanger is a cool trick. I liked it on bass, very rich sounding.

I have played all three and own the first two. The Polychorus is on my board right now, and it’s my go-to effect when I want some modulation and textures, even if they aren’t always traditional. Your mileage may vary! Good luck!

The Small Clone is probably the best chorus you can get. I’ve played a few boss chorus pedals, but nothing compares to the Small Clone.

Vintage Small Clone is at least equal to the CE-1 if you ask me, but I agree it wipes the floor with all the Boss CE-x produced afterwards. You have to hear the DC-2 in stereo though. (I’ve got an old DC-2 and also one of the first run of John Fromel’s Lush/Seraph clones, which is better again).
Chorus got horribly overused in the 80s and it still makes me cringe a bit…but of the ones listed, I don’t think you can go wrong with a Small Clone if you’re after classic chorus sounds.

I personally prefer the Deluxe Electric Mistress as a chorus pedal, it’s well lush!