We loved both Vietnam and China. I think Vietnam meets your requirements of unique shopping goods which aren't found anywhere else - some of the home wares for sale in Hoi An were gorgeous.
The nightlife in Vietnam is quite low key, there is nice food and restaurants, lots of history and places of interest to see between the north and south. It would seem a shame to go to China and only see Beijing, as southern and central China are also worth seeing and worthy of a longer trip. Also I think Vietnam is easier to 'get into' straight away as even though we are used to travelling, China was still a bit of a culture shock and took us a while to get used to!
As you mentioned your honeymoon was a 2 week holiday, I assumed that you would be spending the same amount of time on your holiday this time? You would be able to skip through the highlights of Vietnam - taking internal flights if you want to or overnight trains. Start in the north in Hanoi (do a Halong Bay junk cruise!) and head to Hoi An, and then further south to Nha Trang, Mui Ne and finally end in Saigon (sorry, Ho Chi Minh City). It would an interesting and fun holiday with lots of culture and history!
Hope this helps!
[ Edit: Edited on 29-Jan-2010, at 04:19 by loubylou ]