What is the difference between Protect and Detect?

From Bulbapedia:

Detect's technical mechanics, including formulas, glitches, and exceptions, function identically to Protect in all generations.

So yes, they're practically the same move.

The only difference I see, besides PP amount and type as you wrote, is that they have a different behaviour in Contests:

• Protect is a Cute move, it rises Appeal by 1 unit in normal Contests and by 2 units in Constest Spectaculars.

• Detect is a Cool move, it rises Appeal by 2 units in normal Contests and by 1 unit in Constest Spectaculars.

And, of course, Protect has its own technical machine, TM17.
Detect has none.