I've recently tried many of the Vietnamese restaurants in Northbridge in search of the best pho. There are some excellent ones out there, in fact they were all serving pretty good pho.
The Tra Vinh however, came out on top for the following. The broth had the edge on the others for its aroma and clarity. Servings of meats was a little more generous with ample side servings of sprouts and fresh herbs. Additonally, all the usual condiments are on every table, not the case with some where the waitresses bring the condiments to the table when they remember to. The complimentary flask of tea is also a bonus.
If you are looking for a restaurant with decor and atmosphere, this is not the place to go. It's more of a cafe/lunch bar, the layout being long and narrow. There is a continuous table down the centre where you can plonk yourself down anywhere or you may choose a table on your own down either side. The service is friendly and efficient and there are always expats eating there.
If you are serious about your pho, Tra Vinh is the one!
This review is the subjective opinion of a TripAdvisor member and not of TripAdvisor LLC.