I have compared both. The 17x11" is a little sharper on shallow targets, particularly if you get over the sweet spot of the coil (this can vary as with all ellipticals).
The 14" round I found to run a little smoother, and may have a bees whisker more depth once target size exceeds approx. 1.5g (this would highly depend on the shape of the nugget). The 17x11 does have a slight edge on species, and iron coated nuggies.
I have a couple of used Elites up for grabs at the moment if anyone is interested.
14" - $280
17x11" very good condition with original box, coil bag and extra skid plate - $320