[Jims5543]

Bench press is going to isolate a small group of muscles, Pecks, triceps will get the bulk of the workout, other upper body parts will benefit as well, shoulders, traps, and back muscles.

Push up will incorporate many more muscles as well as strengthen your core muscles.

If I had to pick just one to do I would pick push up, if you can vary between the two then even better.

My workout incorporates both.