Decode the initials
EDT means eau de toilette; EDP means eau de parfum. Cologne and parfum/extrait are other common descriptions. These terms generally indicate concentration categories, but ranges overlap between brands.
Compare the actual versions
An EDP is not necessarily an EDT with extra fragrance oil. The composition can change. Read the exact product name and notes before comparing two versions of a familiar perfume.
Do not promise hours from a label
Wear, projection and your perception depend on the composition, amount and conditions. A concentration label alone cannot guarantee how long you will smell it.
Your practice
Try the exact versions separately, using a consistent amount. Keep notes on the opening and later impression instead of declaring a winner at the first sniff.