I used to go to Ben Tre for lunch when I lost Vien Dong on Clark, and after Pasteur became too "commercial" and Le Colonial too expensive. Ben Tre's lemongrass chicken is very flavorful. But I switched to Hoahn Long a couple of years ago and the idea of going back to Ben Tre would never come to my mind...
By the way when you compare the number of guests, especially those of Vietnamese descent, at the two restaurants at lunch time, you will rapidly get the picture... One of them, Ben Tre, is often empty and the other one quite busy.
By the way Hoahn Long is located on the same site where one of the greatest Chinese restaurants this city ever had, Peter Lo's, was providing its very tastebud-stimulating dishes 30 years ago.
I tried many Vietnamese restaurants in Chicago since the early seventies, and even though I'm still convinced that that there is not a single really great Vietnamese eatery in Chicago, like those hat you would find in Paris or Montreal, HoanH Long is quite satisfying and more than reasonable in terms of cost per meal.