Although I can't give you the exact details, I had the mid-price upgrade done to mine and it came back much better. The reception was better, it didn't go through batteries as fast, the LCD was a brighter white and the battery contacts were a brass color, not silver. I'm pleased with it. I'm getting ready to send in my PSR-800. To me, it was well worth the money.
P25, you'll now have P25 phase I & II and DMR, that alone is worth it AND you get a number of updates making it a WS-1080 in a RS case. Well worth it! Remember you'll need EZ-Scan as well (for the WS-1080)!