I'm not really sure of the details, but just going from my impession of both places I think it would depend a lot on the individual Jarl. Cyrodiil seems pretty evenly proportioned as far as territory and authority of each Count whereas Jarl could either be a big deal or not much depending on the person's holdings and ambition. There'd be a big difference between, say, Jarl of Morthal and Jarl of Windhelm, but even the smaller ones have had their chance at greater glory. The Jarl of Falkreath might not look like they have a lot compared to a Count, but one managed to take over the Imperial City and had Talos as his general, for instance.

Five minutes ago, I would have chosen the Jarl, but Death-Of-Uriel got me thinking. Thank you for pointing out a lot of stuff.

Oh, and wasn't the count of Leyawiin pretty much fighting a war against some Khajiit in Elsweyr? I don't quite remember.

Also: The situation may have changed drastically within the last 200 years. Cyrodiil pretty much broke apart, Bravil and Leyawiin waging war against each other and stuff!