This was covered in a recent MT ;
898 supports PL and DCS (895 only supported PL, and not all of the standard codes), and decodes much faster than the 895
898 supports changing the mode in the 138-144 mhz mil mobile band (895 didn't)
500 channels in the 898 vs. 300 in the 895
the 898 does scan somewhat slower than the 895
the 898 includes the new 6.25 khz spacing that some VHF systems will be moving to (the 895 doesn't)
10 search ranges (the 895 had only 1)
Attenuator (the 895 didn't have it)
Industry standard DB9 on the 898 rather than the 5 pin oddball that's on the back of the 895
That should just about do it; you might also want to search EHam and see if someone has written the scanner up (surely by now someone has), and there is at least 1 Yahoo group devoted to it as well.
73s Mike