Yes, you are right, the main features are the same as in DC-Time engine. PT is more accurate and has some additional features which enables you to easy your design timing check (eg. to show violated paths graphically) and is much faster then DC-Time engine. I am using PT in most cases for post layout timing checks (with backannotated SDF files, which includes real cell and net arc delays). If I have possibility to chose PT or DC for timing checks, I will always use PT. But for smaller designs maybe you can also use DC for your timing checks....