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.
Pricing model
WonderKit prices per group, not per seat. TripIt charges every traveler.
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.