Since Kobe airport doesn't really have direct rail access to Osaka, I'd recommend flying to KIX or ITM. If you do use UKB, you will have to make at least one change or more to get to Osaka.

ITM has bus or rail access to Osaka and KIX has the excellent Japan Rail "Haruka" that stops at multiple points in and around Osaka as well as local trains direct to the major downtown stations.

EDIT. Once again, we were typing at the same time. Great minds and all that.