I've used both the Hornady and the Sierra 220 gr bullets.  I've been using the Sierras in local matches this year, but I'm bringing the Hornady to Camp Perry as I think my Krag is slightly more accurate with them.  Personally, I prefer the Hornady as the bullet profile is more of a RN shape, where as the Sierra is more tapered with a smaller nose... but as reincarnated stated, we use what we can get.  Hornady considers the 220 RN a seasonal bullet these days, so they only run them occasionally.  I stock up when I can find them.  Right now, they seem to be available (Cabelas had several boxes of 100 in stock this weekend).