I had a 2008 L320 (2.7 TDV6) from new for three years and have now owned a L322 2010 3.6 TDV8 for the last 3 years. I was also loaned a pre-facelift 2009 L320 TDV8 for a few weeks, then a brand new just launched facelift 3.0 L320 for a week or so when my 2.7 L320 was having warranty work done back in the day, and my view is you need to drive both L322 and L320 to be sure which you personally prefer as they are almost chalk and cheese.
In my opinion you can go for an early TDV8 L320 or 2010 facelift TDV8 - they didn't do the TDV8 in the 2011 (I wouldn't go for either the 2.7 or 3.0), but the big difference in my view regardless of engine is the wheelbase and construct - The L320 being a shorter D3/D4 Body on Chassis architecture, and the L322 being Monocoque. So they are different in the way they drive, but mostly because of the wheelbase.
I personally find the L322 more than 'sporty' enough for me, but not too 'twitchy' on the longer drives, and therefore wouldn't go back to a L320. Having also owned many European Coupe's/sports cars (my L320 2.7 was my first 4 door car in 15 years) - its the best daily driver I've had.
I would personally recommend a 2010 3.6 TDV8 as a minimum for the updated interior, and 'toys' - and if you do go this path try and get the Luxury if not AB so you also get the heated/cooled seats. (you also only get heated seats on the higher spec L320's AFAIK). If you get the L322 4.4 TDV8, you can only have 19" or 20" wheels. With the 3.6 you can buy 18" Compomotive wheels to give you extra sidewall obviously! (I'm still on 20's but looking to move to 18" for offroading/camping). If you don't need the 18's and can stretch $'s I think the 4.4 TDV8 L322 Luxury or Autobiography is the car to have IMHO.
Just my opinions and hope they help in someway.
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