Depends on how much stuff you're lugging around with you. If you have heavy luggage, four transfers will be no picnic (especially the transfers to and from the shinkansen). Taking a domestic flight would bring the number of transfers down to two, and then it would just be a matter of taking stuff from baggage claim to curbside, then back to check-in.

With light luggage, I would definitely take the trains all the way from KIX to NRT. Very comfortable and you get to experience the cities and the Japanese countryside a bit.