Gulp and Trigger X are very similar in that they are both scent infused baits. I have used both and each seems to work well. I believe Gulp is infused with fish attractants (ie. food) while Trigger X is infused with fish feeding pheromones.
Pros of Gulp – Cheaper, more colors/styles of baits
Cons of Gulp – Cheaper (softer) plastic so it doesn’t handle the repeated bite as well as Trigger but it’s still adequate.
Pros of Trigger – One bait will last for dozens and dozens of fish. Very strong
Cons – Price is a bit higher for only 6-8 pieces. If you leave it on your hook after fishing it is nearly impossible to remove. Similar thing with gulp but not quite as bad.
Take all for what it’s worth, just my experiences and info off hand.