As mentioned in other replies...
If in doubt, try listening to all of these units in an A/B environment, where everything outside of the workstation is equal.
Every sound engineer (studio or live) that I know (and I know a bunch, and I am one as well) picks the ES over everything else... ESPECIALLY when doing an A/B comparison... even completely dry, with no onboard effects applied.
With that said, I would also say that user interface can be an issue as well. The ES certainly has a learning curve, but once you get it, you've got it. I was never impressed with the Triton... and watching the President of Korg fumble around, and ultimately fail at getting the desired sound from the Triton didn't do anything to impress me either. This was on stage at BB King's club in NYC at MoogFest (May 18, 04). After he gave up, they used a Motif-8 instead.
My own opinion is: find something that YOU like... that is a good 'all purpose' workstation which doesn't sound weak and wimpy, and then settle-in with it for a while. Trying to keep up with the latest and greatest will drive you crazy, and deplete your bank account. No matter what you buy, within 6 months, it will be old news. You'll either end up with dozens and dozens of systems/keys/synths... whatever, or, you'll end up trading in or selling off stuff every time the next little gem is released.
I'll be buying my next workstation when: 1. It does everything I want by reading my mind; 2. It costs about $1k; and 3. It wipes my a$$ for me. I'm actually having alot more fun expanding my modular system than keeping up with the latest digital brew-ha-ha. At least with a modular, you put in the modules you want... you can expand almost infinitely... you can buy or build 3rd party modules... you can trade and/or sell modules, you can make sounds that no one has ever heard before (as opposed to canned factory patches, samples, and sounds)(i.e.- something that someone else has done)... and you have analog control. Plus... when you come up with a truely way-kewel sound, you sample it for use in the digital world. I truely dislike some aspects of digital, menu-driven anything... and the reason is, you can only control what's on the open menu page at any one time. The Motif gives you some control of parameters (4 knobs, and 4 sliders)... and the Korg MS-2000 & 2000b are good examples of trying to combine digital presets with analog controls... and yes, there are other examples too.
[wOw... did I say all of that?]
At any rate... when I was in the market for a digital recorder for my home studio, I ended up buying the Yamaha AW-4416. At the time, for the money and features, specs, and size, it was the best deal going. I have gotten alot of milage out of it, and plan of keeping it for a year or two longer, and let the evolution continue for a while. It's replacement will have more tracks, real faders & knobs for everything, automation, plenty of onboard effects... and so on, but I doubt that I'll ever use a keyboard workstation as my main recorder, and certainly not a pc-based recorder. For those of you who will say: "yeah... but pc-based programs give you zillions of tracks"... you guys don't know what you're talking about. Anyone who knows anything about recording engineering knows that there is a limit to the number of tracks that is practical. I'm sure one could easily come up with software that gives you 1,000 tracks. That would be problematic on it's very best day. Less is more. The more bells & whistles you have, the more problematic it becomes. Go for good sound. Go for easy to work with. Go for flexability.
Of course, this is all just my opinion. But I have been refining my opinion(s) while working in the music biz both as an engineer, and a synth/keyboard player for 30+ years. It seems like as quickly as technology is evolving, it almost makes since to just rent something for 3 or 4 months, then turn it in and rent the next 'latest & greatest'.
Ok... I'll shut up now.
