Wirelessly posted (BlackBerry8330/4.5.0.169 Profile/MIDP-2.0 Configuration/CLDC-1.1 VendorID/126)
The 5000 and 2500 are essentially the same thing.
The 2500 can not have user-selectable high/low power - these must be hardcoded in the personality.
The 2500 isn't capable of Type I encryption algorithms.
Also, the 2500 doesn't do the Fireground Accountability system. Note: this *can* be put into a 2500, but Motorola won't officially support this, any 2500 with this feature did *not* come from Motorola.
Also, the 2500 does 512 modes, the 5000 does 1000. However these are soft limitations. Both are theoratically capable of 2048 channels although again, this isn't a Motorola supported feature so you aren't likely to find one that does.
That's pretty much the differences, besides physical ones and battery types.