15x7 is THE size if you want the best handling out of your escort, hands down. If ultra-low profile rims really gave a huge advantage to handling, you'd see national autoX and roadrace winners using them all the time. low-pro can help a little, but there is a diminishing return. remember, for each 1lb of mass that a rim weighs, the drivetrain sees it as 5-8 lbs. now add a larger diameter, with heavier tires to match, and you've got a hell of a lot of added weight at a further distance from the axle. that means it takes longer to stop and longer to start, and taken to extremes, even longer to change direction.
Sure, you'll see 'vettes and other similar-performing cars with really low-profile 18's, but they're 335/35-18's and other similar sizes, not narrow like 245/30-18's, and their sidewalls flex a LOT more than the narrow ones do, just because of the force that is being exerted on them by a huge-ass patch of rubber on the road.
bottom line, determine what you want your car for, looks or performance, then go with the best of that choice. Compromise is ALWAYS less than 100%.
--sarge