There are definitely dumb OS Giants out there. I have a blue VIP that is just a hoss, makes my pink VIP Giant look like a TL. They're a good deal more OS than a Trespass, and faster.
I'd say Giants are like new Champ Destroyers, some meathooks, some usefully OS, and Trespasses are like fresh to beat Star Destros. I carry a VIP Giant for HW duty and a beat Fuzion Trespass for a stable disc on water holes and they're pretty complementary. Giant-Trespass-Destiny-flippy King is my distance lineup and it works well (except my Destiny might be seasoning into overlap territory with my King).
Never thrown a Boatman so I can't help you there.