I believe the EM25 has 1 meg wave ROM (same as the EM10), and the EXR-5 has an 8 meg wave ROM. That is a substantial difference, that you have unmistakenly noticed. When I demoed the EM10 about 3 years ago, I was not impressed, but was impressed by the EM20 which has 8 megs wave ROM. It sounded about 8 times better (that's logical), with more voices as well. Would have been appropriate for Roland to increase the wave ROM since it is an upgrade to the EM20/EM30/EM50 series.
Also looking forward to Fran's review.
Starkeeper