We're looking to see the inside passage and are considering either the Radison Mariner or the siver Seas Sliver Shadow. Any thoughts out there which one.

Having just returned from the Regent Seven Seas from Vancouver, BC to Whittier, AK. I can only state that the ship rated a 9.5 overall (on a scale of 10). I have not sailed Silversea yet, but Regent is comparable, if not more relaxed, than Crystal. I posted a topic called 10 Things about Regent today and have more information if needed.
Sounds like that either choice, you will truly enjoy a luxurious trip.

Keep in mind that

• Silver Sea is all-inclusive whereas Crystal is not - but, with comparable pricing.
  
• Regent provides complimentary liquor in your suite and Crystal does not.
  
• Regent provides wine at dinner and Crystal does not.
  
• Regent is going all-inclusive in 2007.
  
• Regent has open seating, Crystal does not.
• Crystal has the BEST mushroom soup (at Prego) in all of the cruising world.