I personally don't think its a matter of hard or ease. But yet patience, that you do need. I had no problem getting my set to lvl 70 in Ruby. Sapphire seems to be abit harder. Playing Emerald now, and lvling in that doesn't take as long. Match Call ftw, specially with the Gym Leaders. The sky Pillar in R/S is a great place to go, with or w/o Exp Share. High lvl Claydols, Sableyes, and more. Give decent exp. And of course, before then you got Victory Road.
Patience though, lots of it, and boredum. lol.
Goodluck.