I suppose that's largely due to your driving characteristics, and whether or not most of your commuting is within the city. According to official EPA figures the F Pace delivers 29mpg combined, while the E Pace delivers 24mpg.
The E-Pace actually weighs a bit less from what I recall, around 100 pounds. Think it's the engine because the F-Pace is offered with a turbo and those are usually more fuel efficient than something like an inline-four. This is just a guess on my end.
They both utilize a 2.0 liter turbocharged 4 cylinder, but the F Pace has an additional 50 hp on tap. I think despite the significant differences in size, they haven't maximized on the engine tune or weight reduction in the E Pace.
Not looking good for Jaguar with the E-Pace. Already there are poor reviews that reflect its poor economy.
Lucky for them its the perfect candidate for a hybrid powertrain that could very well save it.