Not sexy by any means, but spreadsheets are no-fuss and allow for the flexibility of including all the nitty gritty details of trip-planning, budget calculations, and tweaking things on the fly.
Ranked in these QuestionsQuestion Ranking
Pro Scalable, customized organization
Infinite row/columns and all the separate tabs to play with. Trips can be organized with as many attributes and calculations as you see fit.
Pro Good for budgeting
Since it is a spreadsheet, very easy to calculate budget, and any secondary calculations as well (e.g. cost/day, cost/location, etc.)
Pro Easy to share
Google Sheets are always accessible on the cloud, and easy to control permissions to share with relevant parties.
Pro Easy to export
Physically (printing) and otherwise (converting to excel, attaching to emails).
Can be accessed from any device via the browser, or Google's iOS and Android apps.
Con Not optimized for travel
Unlike travel-specific websites, Sheets won't be able to tell if one link is a flight, and another is a hotel reservation, nor will it be able to know which cells correspond to what leg of the trip.
Con Zero foundation
While there are sample layouts (see Travel planner), it's likely that each person's trip planning needs will be unique enough that it's better to start from scratch. Of course, once you use Sheets for one trip, it'll be easier and faster to set it up for future trips.