Seriously, I have been badgered for these numbers since day one.
Not just hypertuned mounts (as no other tuner seems to publish any data...), but ALL equatorial mounts and to compare them online. It makes it easier when making decisions about which one to buy. Or is it that easy? Of course not, this is Astronomy!
Now let us manage a little expectation here. Any mount that can guide via an ST4 port 'should' guide when properly set up down to circa 2 arcseconds, which discussed elsewhere is enough for longer exposures under UK skies. Well, under any skies actually. Oh, it needs to do it with your telescope of choice, DLSR or CCD, guidescope and guide
camera. This is where it gets a bit fuzzy but I'll simplify where I can. Primarily, it's all about how it's assembled, and designed. With guiding, some mounts are more equal than others.
The common rule of thumb is to take off 1/2 to a 1/3 of the stated maximum payload of the mount, if you're astro-imaging. S'not fair you cry! But it makes sense. Sort of. This applies to any worm-driven EQ mount, and should be set up slightly east-heavy to provide the mount with an attitude of a controlled fall, so that the RA motor is dictating that precise movement. Your guider by looking at a star dictates sidereal movement, that your motor corrects to.
Have a read of this data table: http://lambermont.dyndns.org/astro/pe.html
This list which has been around for awhile lists over 120 mounts stated and independently quoted via owners and forums. It's not quite up to date but illustrates cost in Euros, Payload (max), Period Error (PE) and after PEC training or other control. There's no quoted guide performance here as it doesn't account for that, but useful none the less. If you mount is'nt in the tables below then try here.
So why is guiding such a mixed bag? Guiding is needed for exposures longer than 60 sec and EQ mount with a lens or telescope over 400mm focal length. The best I got unguided was 8 mins unguided at 320mm fl lens and Canon EOS450D on a Sky-Watcher Star Adventurer, and also using an AstroTrac TT320X-AG. However, that's because it's light and my Polar Alignment was god-like (it normally is, but I also have to work on my modesty), after 15 minutes of tweaking. Start using a small 70mm refractor even at f4.8, or a 150mm f5 Newtonian and it will start to fall apart quite quickly. Auto-guide and your exposures are transformed from 1 minute to 5, 10 or even 20 minute exposures. As you do this your signal to noise ratio drops, and you are rewarded with more detail and resolution as you gather more of those much travelled photons. However, weather dictates all.