Not dumb at all. We did the shore dive on our own and I think there were several factors that played a role. First off, the walk in and out is pretty extensive, so we were probably breathing heavier than we were from the boat entry. Plus, not knowing exactly how long the shore exit would take led us to be somewhat conservative with our air supply to have reserves for contingencies. Both of those combined for a shorter dive time. (And we were hungry too, so we traded some bottom time for lunchtime.
)
From the shore, we started on the shallower part of the pier. None of it's deep, but we did burn a little time on the shallower portions going in and out. Also, because of the time/air considerations already mentioned, we didn't make it out to the very end of the pier. If I had to guess, we got 3/4 of the way down on the shore dive.
Part of it was luck too. On the shore dive, we did get to see turtles, imperial nudi trains, and lots of reef fish, but we didn't come across the sharks we had hoped for.
With a guide from the boat, we had much longer bottom time, plus we started from the deepest parts of the wharf and the guide knew the highest probability areas to take us. We still got turtles and nudis, plus we got some great shark encounters and through a combination of the guide having the experience to know to take us out across the sand flats a bit and simply being in the right place at the right time, got to see one of the coolest things I've seen in my 17 years of diving, two huge frogfish sashaying across the sand a couple of feet away from us.
Here's a video of that. Fair warning, it's shot with ambient light and no filters and is completely unedited, so a tad long, but it's easy enough to click forward now and then so you don't have to watch the whole thing:
Sorry for the essay answer there, lol. Either way you're going to have a great dive. I'm very glad I did it both ways. IMO, if you're going all of the way to HI and want to see Mala Pier, spend a little extra and maximize your experience there by doing a guided boat dive.