I've eaten at lots of Vietnamese restaurants east of the Mississippi. I have found them as a group to be more variable than Chinese and Thai. Not in terms of quality but in terms of flavors. Some serve food indistinguishable from Chinese, some serve food clearly related to Chinese but with very interesting and often delicious twists. Personally, the most disappointing have been those most indistinguishable from Chinese. When I'm in the mood for Chinese I go to a Chinese restaurant. Bottom line: you won't know what your local restaurant serves until you actually taste it.