Having gone from a 42T round to a 40T oval, the 40T feels easier as a 40T should being that its two less teeth, but it does spin over a lot easier than I thought it would, and it does spin over a lot quicker than my Absolute Black rings that I have on other bikes.
This is my first go with Wolf Tooth's "PowerTrac Elliptical" Which I guess is suppose to not be as dramatic of an oval as other brands.
I'd say that its not worth trying, or even getting the same size ring as you're currently running.
Personally, I like the oval rings, I do see a performance benefit with it over the round rings in that I don't have problems with cramping with it, as opposed to the 42T round ring I was using before, and this isn't just this time. I've had problems with cramping before that "mysteriously" disappeared when switching to an oval ring. I don't have any other substantiating evidence to support this, but it does seem to be the case, at least for me.