Choosing a 2005 ML?

My transmission blew up on my 99 ML430 at 127k miles (the transfer case went out at 90k miles).  So, since its sitting at the stealership as a giant paperweight and they''re offering me 4k on a trade as it sits, I''m considering trading it in on a 2005 ML - any advice on the pros and cons of a 350 vs a 500?  Or am I chasing rainbows sticking with an ML at all? 
 
Tara