Elevated bowls do have some benefits particularly for toy breeds. Eating from an elevated bowl may help dogs that have digestive troubles. Additionally, it puts less strain on a dog's hips, shoulders, neck and joints.
Large breeds that are prone to bloat (stomach torsion) do better with the bowl on floor level. This applies most often to the German Shepard and the Boxer. The Shih Tzu and most other toy and small sized dogs are less prone to this condition; therefore this is less of a concern for this breed. If your Shih Tzu has had previous issue with stomach bloating, you will then want to opt for a floor-level bowl only, for both food and water.
Having a cute elevated bowl set can also help with the issue of food particles and water ending up on a Shih Tzu's face, which can cause staining to the facial hairs. When facial hairs become damp after lapping water and are not dried, this can cause the moistened hairs to become a breeding ground for red yeast which is one of the causes of tear staining.
Finally, older senior dogs tend to do better with a raised feeder as it is easier to eat with less strain on the entire body.
You'll want to make sure to choose one that is specifically for toy breeds so that it is not so high that the Tzu cannot properly reach it.