These two sound similar but solve different problems. Here's the real comparison.
WonderKit is a trip planner. You describe what you want; it generates a day-by-day itinerary you can edit with your group. It doesn't organize bookings — it creates plans.
TripIt is a trip organizer. You forward booking confirmations to it; it stitches them into a timeline and sends you flight alerts. Been around since 2006.
TripIt starts when you have bookings. WonderKit starts when you have an idea. Many travelers use both: plan in WonderKit, organize receipts in TripIt. They don't compete so much as complement.
TripIt has no meaningful group collaboration. If you're coordinating a bachelorette, family reunion, or friend trip, it's not built for that job. WonderKit is.
Flight delay notifications, airport maps, car rental confirmations, terminal info — TripIt Pro's business-traveler feature set is mature. WonderKit doesn't replace that.