I like the slider tuna cord for the ocean and the straits. The spreader bar helps keep your gear from tangling on the way down.
In the straits where you will be drifting and your line is not as straight up and down, I would advise against spreader bars. If your line angle is back aways, spreader bars will drag through the rocks and hang up. The straits are pretty snaggy.
In the ocean where you are fishing 300-600' or deeper is where the spreader bar works better. Straight up and down lets it tap the bottom instead of dragging. You typically use a 2 or 3 pound weight in the ocean. Spreader bars can work great there. But when you bring a fish up, make sure and grab the weight and remove it off of the spreader bar as a halibut is going to whip it around, hitting the boat or you.
They both have there place and I keep both around, but use the tuna slider cord more.
If you want to see them both, I am giving three seminars this week. First one is PSA Eastside in Redmond on Wednesday,
Three Rivers Marine in Woodinville with the best halibut/ling charter out there-Jambo, this Friday night at 7:00 and one Saturday at 3:00 in Friday Harbor for the new PSA San Juans Chapter.