The great difference is that Roland EXRs can't edit styles and has less possibilities, its operative system is very tedious (PSR is much more easy to operate, and has a better screen), and they are less styles for it on the net.
But... EXRs likes more professional, its voices are good, its key feel is a lot better, it has more keys, it is better built, and is less expensive.
So... it depends what you want more.