Hi,
There are several ways to configure your Davis ISS, and the console or Weatherlink Live.
6253 is a VP2 ISS with the 24-Hour FARS so a first upgrade from the basic VP2, and the new 6313 console
6263 is the VP2 ISS with the 24-hour FARS and UV/Solar sensors, and the new 6313 console
Both are a very good upgrade from the basic ISS 6152. I enjoy my 6163 (same as 6263 but with the old console instead of the new colour console).
Other things would depend what you want to do with your data. The 6253 and 6263 can upload to Weatherlink.com (Davis Cloud) but at present has no data logging, data logging in the sense that it can be read and used by third-party programs like CumulusMX. So with the 6252/6253 or 6262/6263 and doing the settings to uploading to WL.com you can view your data there and/or on the Weatherlink App as well as on the 6313 console.
Weatherlink Live can be added for the use by third-party programs on your computer or Pi for the live data stream as well as the logged data at WL.com.
Adding a Davis AirLink is also a nice addition and it can upload to Weatherlink.com and viewable there and on the App, but again it is not yet an option to view it on the 6313 console.
Enjoy,
Paul