I'm really happy with my Ibanez CF-7. Does chorus and flange very well. The flange can go from quite subtle to over-the-top jet-plane like sounds very easily. Lots you can do with them, and they're built like tanks -- every bit as tough as my Boss pedals.
I don't think the FL-9 gets too close to the DEM. Both are a really thick flange, but the FL-9 is more aggressive and "crude" sounding, not as pretty as the mistress can be. The defining feature of the electric mistress is the little warble it has at the ends of the sweeps. The FL-9 doesn't do that.
I'm not sure what to tell you. I'm a BIG flange fan, but I still haven't found the "perfect" flanger. I don't care for any of the Boss options. I think the MXR is too dark sounding. I've never tried an ADA, but they are rare and expensive. DEM sounds GREAT to me, but it's huge and can be noisy (clock noise! blegh!!!) -- and doesn't have as much manual control as some of the others.
The stereo electric mistress doesn't sound anywhere near as good to me as does the DEM, and doesn't have as much manual control of the sound. And if I wanted chorus AND flange I'd use a chorus pedal after a flanger. I don't really want them on the same pedal.
Flanger hoax is huge and apparently hard to dial in. I don't want my flanger pedal to do phasing, I want classic flange!!
I've never tried some of the more exotic options like the foxrox or the lovetone, but I understand they are more useful for crazy sounds than they are for classic flange tones. The lovetone is too hard to find and too expensive. the foxrox TZF often sounds ugly to me in clips, and very dark sounding -- and it is reputed to be very subtle which is NOT what I'm looking for. I like flange on clean sounds and pre-overdrive, and the TZF reputedly does not excel at those scenarios.
I was all excited about the Toadworks Barracuda, but the delays in it coming out are deflating me, and the soundclips they finally posted on their website did not do it for me. I'm anxious to try it out for myself.
The BYOC looks promising, but it was supposed to be out last fall and there's still no new news on it. Last I heard it was being redesigned? It's supposed to be a mash-up of features from the MXR and the A/DA circuits, in stereo. Interesting... but when will it be out, and I'm not sure I can trust anything I have to build myself!
I just ordered a rocktron hypnotic flange. I have high hopes... It was stupid cheap and is supposed to be based on analog BBD. It also has a mix control which I think is a great feature. I like the sound clips I've heard of it, but I can't find a local shop who's got one -- but I figured it was cheap enough to give it a go. I'll report back.
+1,000,000 on the TZF, but they can only be bought used right now. The Fulltone Choralflange is the best I have found to equal the tone of Electric Mistress. Fulltone recently upgraded the flange side of this pedal.