Just a couple of comments here, joining the discussion late. I use an Ebony SV45U and RW45 in the 4x5 format, and a SV810 with 5x7 and 4x5 reducing backs.
Asymmetric movements add almost no weight. The difference is the thicker swing plates to accomodate the dovetails that the asymmetric models utilize. Since the plates are titanium, were talking an ounce, maybe less.
Asymmetric movements don't cost $1,000+ on the 4x5 models. The difference at Badger Graphic between a SV45U and a SV45TE is $500.
Asymmetric movements make set up time faster if you include composition in the set up time, which you should - and you're using back movements (since the Ebony models don't have asymmetric front movements). It isn't just how fast you can get the camera and lens on the tripod, it's how fast you can take a fully composed photograph if that means anything to you (I've never understood the fascination with speed of getting your camera on the tripod in 15 seconds). It doesn't to me unless at sunrise or sunset when seconds can matter. Asymmetric movements are useful in landscape photography. How useful is a matter of opinion; they are faster, but you can "iterate" a conventional back to achieve the same result.
Asymmetric rear swings bind on large cameras. I returned a SV810UE because of binding. Titanium is a lousy bearing material, and the weight of 5x7 and larger ebony wood rear standards makes for a very unpleasant experience. That's how I ended up with a very nice used SV810, conventional swings in mahogany. I had the UE back at the factory, and this isn't a problem lubrication will help. You can notice it on the 4x5 models but the rear standard is light enough it doesn't matter.
So my advice based on the above is:
If you're a "back movement" person, get the asymmetric 4x5 model, you will never regret it. they'll build you a mahogany version if you want; eventually I'll have them build one for me.
On large models, go with symmetric movements and mahogany.
Steve