They both have their pros and cons. TPU absorbs shock and since it stretches, TPU cases are one piece. PC can take a beating from hard surfaces and slides in and out of the pocket easily. TPU cases tend to stretch over time and PC will crack and is generally, not one piece.
For protection the best case is a hybrid so that it has the pros and not the cons, but the new con for hybrids is bulk. Personally, I like hybrids, but for a slim case I prefer TPU or some type of silicon.