I’ve only sat on one briefly, but the Ty Davis tank, made by IMS I believe, is nearly as thin as the stock YZ tank. IMO it is kind of extreme, you can’t get at the hot start and it appears to block radiator flow a bit more than the other options. Of course, Ty Davis doesn’t seem to have any problems with this :D
I’ve had the std. IMS and the new Acerbis on my YZFs, the IMS is noticeably wider than the Acerbis, which is slightly wider than the Ty Davis tank. As for the “ski jump” effect, I think it is a wash, with all “dez” tanks being a bit taller than the stock YZ tank, but coming from a WR I doubt you would notice since you are moving the ramp forward considerably. :D For me the wideness is more noticeable than the “ski jump” effect, which I’d forgotten about completely after the first couple of minutes coming off a stock YZ tank.
The Acerbis is a bit more expensive than the std. IMS, but you can install a dry break or “normal” filler on the same tank (if you buy the tank and also the dry break kit). Another way of saying this is you have the option to go w/ a dry break in the future w/out having to purchase a new tank, I guess that is the main reason for the (slightly) higher cost. The Davis tank is about the same or a little more than the Acerbis I believe.
I’ve had Devol rad guards with both setups, but I don’t know if the WC style braces will work with any of these oversize tanks on a YZ/WR.
I’ve only seen the Clarke tanks, haven’t even sat on one, but they don’t appear to differ noticeably from the IMS.
You may want to check Thumpertalk for opinions on the Clarke tank, I know several members over there run that one (and the Davis tank is also popular, some good pics of it were posted recently).
Hope this helps.