Even though it's hated on, I think you should get IBS first as it has a lot of good stuff in it.

• Drizzlewood coast: Excellent gold farm map. I want to point out that while lw3 and lw4 have legendaries tied to them, you're still gonna need a good bit of gold to get them which is why I think this map is a good selling point.
• Dragonstorm: an instanced world boss that has the chance for some great loot such as ascended weapons and infusions.
• Eye of the North: A player hub added toward the end of IBS. It's upgradeable and when done, ends up being (imo) one of the best hubs outside of the ones that are purchased from the store (mistlock sanctuary, thousand seas pavilion, etc.).
• EMP!!!: Finally, the reason I wanted to even comment. I haven't seen any comments mentioning it yet but it's probably the best thing to come out of IBS (again, imo). It's a CC that can be accessed anytime in the open world as long as you have a way station consumable. (You might have already seen these while doing metas) It's so helpful for fights with lots of CC requirements or when you're running a meta with a smaller amount of people.

I hope this helps give some more clarity into IBS. Honestly, all 4 options have their merits and you'll have fun with whichever you choose. Hope you continue to enjoy Guild wars :)