well the "main difference" is the P25 decryption, they will each trunk the same systems the 396 will decode P25. Other facts of interest are the BNC vs SMA on the 396. So if this gift is for a current scanner owner, the SMA would need to be adapted to current antenna's possibly.
If your not looking to decode P25 (which only federal gov. uses P25 primary today in NW, and there isnt a bunch of it) I do know that P25 compatible radios are being deployed to LEO so likely that within 2-5 years TAC's and SpcOps will be P25 if not encrypted.
If price is a concern the 246 is a great radio for the NW you can listen to every city major police in WA and OR, I would also recommends getting ARC246 software or checking out the free beta-BCTOOL for programming. The 246 is a nice step into dynamic memory.
if price is no object then spend the extra 300 on the 396 its currently compatible almost everywhere but some places on the east coast. but for the NW there is no need for it for the casual scanner, there arnt any features that are so awesome that the 246 lacks that the 396 has (for the casual scanner, and for your first dynamic memory radio) they each have the close call.
my personal complaints about the 246 are the lack of a backlight for the buttons, the lack of 99 group memories (like the 330/369/996/15 have) other then that its an awesome radio that I have along with a bc15, I do want a 996 for P25 but waiting on GRE's new base to see if its worth the beans. but until 2013 (approx system change over for NW) im not too worried about paying P25 tax since the cheaper analogs will work for 5-7 years
eham reviews on them
http://www.eham.net/reviews/detail/4753http://www.eham.net/reviews/detail/5242