Hi Dave,
The scopes you linked to are very similar but come from different manufacturers. As far as I know the SkyWatcher is a "Synta", whereas the TS is a "Guan Sheng Optical" (GSO) with some modifications. Optically they are probably very similar. Sky at Night magazine did a feature on 200 mm f/4 reflectors in the December 2011 issue, comparing the SkyWatcher, the original GSO, the TS carbon fibre version and the Vixen offering. The SW, GSO and TS scope got identical scores for optics and the SW was declared the overall winner by 1% on the basis of slightly better build and design. It appears that the TS scope had design and build issues, but the version offered now is different, e.g. it has a better focuser. Bottom line is that there is very little to choose between these three brands and the same will probably apply to the 254 mm scopes.
Bear in mind that accurate collimation is not trivial with these very fast Newts and you will need to add some collimation tools to your shopping list. You should also get a Bahtinov mask which makes precise focusing a breeze. I found the straight-through style of finder difficult to use on a Newt so you might consider getting a red dot finder instead. And don't forget power supplies for your mount, guider, and PC. What you need in that regard will depend access to power at your imaging location.
That brings me to one final point that hasn't really been highlighted in this very interesting thread. Do you have easy access to dark skies? If you do (you lucky sod) the whole range of astroimaging targets is available to you. Consider an apo refractor for the large targets such as nebulae (though you will need a modded DSLR or a dedicated astro camera to tackle most emission nebulae) and/or a scope with a longer focal length if you prefer smaller targets such as galaxies - a 254 mm f/4 or f/5 Newtonian is excellent value in that category. How dark your sky is may have a much bigger impact on how long your exposures need to be than whether the scope is f/4 or f/5.
If you do not have dark skies you will find astroimaging frustrating, and in practise you will be restricted to brighter targets such as clusters. Of course, if you have the time and the transport to easily move your gear to a dark site you are in business again. Just keep the transportability of the kit and the power supply factor in mind.
I hope that these extra considerations will help you make the right choice - you are very wise to take your time and do lots of research. Your budget is large enough to put together a very nice setup capable of meeting a range of imaging and visual requirements - good luck with the planning.
Mike
Skywatcher 120 mm ED on a CG5 mount.
Orion UK 300mm Dobsonian
  