Both work fine, but when I'm making the initial FPs for a long trip at the 60 day mark I think it's easier to see what I'm doing on the computer. This is especially true if I'm making FPs for multiple people who aren't consistently all doing the same attractions (some want to ride one thing and others want to do something different at overlapping times). It can get confusing on the phone because it's harder to view what you've already done as you're working on the next pick. It's just generally easier to look at the group itinerary online. The phone is great for making changes though, and for adding additional (4th or more) FPs on the day of.