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.
"Good girls go to heaven, bad girls go everywhere"---Helen Gurley Brown