Is there really that much of a difference? the only one I know of is the weight. Oh and price.

My first wasn't carbon, my second will be. The lighter weight makes a tiny bit trickier, but I think more fun. And less to carry of course.

This guy does a great job reviewing gear. Read the article and below in the comments as per they relate to your question.

thewavehobbit.wordpress.com/stand-up-paddle-boarding-s-u-p/articles/the-battle-of-the-fanatic-pro-waves-82-2012-v-8-2013/

The main difference is what you mention weight and price!!

If you want to get in to training then go carbon as that little extra pick up you get from the lightness is sometimes that little extra edge you need and over a long distance you can start to really notice it.

If its just for general paddling and fitness then the HRS is fine and will do the job nicely and saving the few extra dollars is a extra bonus!!

Carbon can look very 2nd hand very quickly.

If you're not going to be really particular loading, unloading, carrying, storing, & paddling a carbon board, be warned - any bump or paddle strike can result in a chip or a crack.

If you're not going to be doing serious racing, and you can manage the extra weight of the non-carbon board, save yourself the cash and go for the more durable HRS/EPS option.