I have a crf hybrid and My friend has the crf bike... My cousin has the X.. .. Honda had the TERRIBLE idea of putting Ti intake valves.. those will clap out if you don't keep them adjusted... Don't let that scare you.. the modern 4-strokes are not 1/16th bad as the myth claims... take care of it and it will take care of you...
As for the bike itself... It's a trail bike.. top heavy, like 30lbs heavier than the crf.. different cam/flywheel/subframe/set/plastic... Basically a totally different bike.. You can ride it literally for days at time ... If your looking to hit doubles.. go with the R....
I can tell you one thing.. when my cousin rode with my buddy and I.... he wished he had the crf half way through the day...
EDIT: With a pipe/filter, gearing, cam and brass balls 100+ is EASILY obtainable... I'ts already got a mellow cam.. throw some fat motard tires on there and let er eat ....
Mike