The celestrons are sold with the 45 degree diagonals because they are marketed for terrestrial use (no idea why though, as it looks like a nice astro scope).
Everything that has been said is true. You get more accessories, a smaller tube but its heavier, a better looking and better made one, a better focuser, better warranty, and a better price. Thats more then enough to choose the celestron. I've heard of orion ED80s being out of collimation. While the celestron hasnt been too popular, i've yet to hear anything bad.
BTW, if you dont like f/7.5 (i know i wouldnt) then go to http://www.scopestuff.com/ss_tasct.htm and pick up that adaptor. That will allow you to use SCT threaded accessories on the refractor. Then pick up the meade or celestron focal reducer and you'll have a f/4.7 and a shorter focal length. Im doing the same thing, though all refractors are different and there is no way to tell what kind of field curvature or other problems you might get. With the extra celestron accessories you get you could sell them off, and if the reducer thing doesnt work, sell that off too, and you've broken even or made the ED80 cost you less.