the FCR just reads and clears faults...
the Extreme gives you 'Superuser' control over the vehicle allowing you to program the Body Control Unit and change settings.
The ability to read live data, Calibrate the suspension, actuate functions for diagnostic testing etc....it truly is the muts danglies...
As for the Hawkeye, it is very good, but has limitations i.e. it cannot calibrate the suspension settings, and the live data is a little sparse.
BBS do do a Nanocom evolution for the later L322's post 2006 I believe.
For 2002-2005 there is the All Comms, but this is just a fault reader with the ability to calibrate the suspension and do minor tweaks.
Then there is the IIDTool from Gap Diagnostics....very capable and neat little package - is VIN locked so will only work on one vehicle and relies on a working message centre display on the dash.
The Hawkeye is again VIN locked....as above
The Lynx from Britpart/Omnitec has received mixed reviews - no experience of it I am afraid to comment.
Then you have th Snap On Solus Ultra and Pro - not dedicated LR units so there could be compatability issues and the cost is large.
The Faultmate Extreme is around £1000 but is fantastic.
I use the All Comms as it is very capable nd does exactly what I need it to do....I can also use it on other peoples L322's as it is not VIN locked like the Extreme, Hawkeye and IIDTool...