The Seahorse box is similar to the Pelican box, but the Pelican costs a couple extra $$
The Pelican is a better box and is worth the extra cash.
The Seahorse box has weak latches, small seals, and an overall "cheap" feel to it. The Seahorse box I tested has no built-in locks, but from the quality of the latches I'd say the locks would pop open with a small screwdriver.
On the positive side, the smallest Seahorse model will accomodate the Owl PF mounted across its smaller dimension without modification. With the smallest Pelican box you have to trim the Owl PF to fit that way.