I've been looking into both as well, but I would use it more for general indoor/outdoor house cleaning. Car detailing would just be a bonus and far less frequent application.
Once I found out the requirement for a large (and not particularly portable) compressor for the Tornador (combined with the fact that the company seems to have decided they should remove any disclosure of information on air flow volume because it will scare some people from buying it), I've pretty much crossed the Tornado products off my list.
Of course, deciding on the steamer as the more versatile for my purposes doesn't really narrow the decision field all that much. There are dozens of vapor steamers with a wide range of capabilities and prices.
It's equally challenging to figure out how much difference a 50 psi steamer, all the way up to around 145 psi, makes in cleaning effectiveness and sanitizing. Then there's also the steam temperature at the nozzle tip, which seems to vary over about a 80*F range depending on model (for models that can operate on a single 20A circuit, or better yet 15A). And finally there's the question of how much having chemical injection helps.
You can get well over a $grand pretty easily.
It makes me wonder if it might be way cheaper and just as effective if I just get:
>>A heat gun with digital temperature setting, set to 300*F or so.
>>A hand pump-spray bottle with either water or solution.
>>A sponge and rag.
>>And for some of the more dirty cases, a wet vac (on the theory that the psi of a steamer and the suction of a vacuum serve essentially the same purpose, except the steamer psi just displaces the dirt and you still have to wipe it, whereas the vacuum contains it all in one step).
So you'd pre-treat the dirt with the pump sprayer and brush agitation, hit it with the heat gun to increase cleaning effectiveness especially for sticky or greasy dirt, and wipe (or vacuum) the loosened dirt. Or maybe you could skip the heat gun step in most cases and just take your container of water/solution and microwave it for about 60-90 seconds.