The difference is night and day. The 996 P2 is it good radio, always was but getting long in the tooth now. The sds200 is the latest release. As described above it has an SDR chip and it can handle simulcast Distortion secondary to LSM very well.
It has a data card that can be replaced giving it much more space including a database in the radio that can be searched just by putting in your ZIP code, then you set the range and how far you want to search.
The display is terrific and very customizable. Different colors, cluttered or clean, white text on black background. It's worth the extra money and even if you don't deal with a lot of simulcast right now it future proofs you.
It's a pretty steep learning curve if you never owned the x36 but you have your ticket and should be able to figure it out just fine. Plenty of reading to do here on the site. Good luck.