As always, to each his own, but:Do both. Do an early morning dive. Clean and hung up your gear and go to the park. Take the short route (still 3 hrs). The long route is too much for us. Have stuff ready the night before (sandwiches, snacks....frozen water bottles).
To me, the short route misses some of the best parts of the park. But, as you say, the long route would be too much for a half day excursion after diving elsewhere. One would feel rushed and not have time to explore all the highlights and savour the experience. You have to allow time to walk around, view the sights, play in the sea, relax and picnic, otherwise it is just a 4 hour bumpy drive. So make a choice. Either make a day of it or do something else instead. The half day rush job is only ticking a box and in all likelihood will not give a very positive impression of the park.
But again, just my opinion.