The short version
Thanh Xuan is a central south family and apartment district where universities, hospitals and arterial roads sit close to the core. It is useful rather than graceful. Residents get a large supply of services and housing, but major roads make walking and quiet bedrooms a matter of careful selection.
The lanes behind Nguyen Trai and the university areas are more liveable than the frontages. Towers offer convenience and managed access, while older streets keep the local market rhythm. Check traffic noise, parking and the final crossing to work or school. These details are more decisive than the district label.
Thanh Xuan is a strong practical base for people whose daily life is south or west of the centre. I would choose a side street and accept the traffic as the price of central convenience.