The advantage of Planner is that it integrates with your MS Product suite, such as Tasks, Outlook, OneNote, and email. By virtue of this tight integration Planner is almost always a preferred option if you're not looking for bells and whistles, and the dedicated mobile application makes it extremely easy to use.
You can use the Kanban board in any manner that floats your boat. We use the typical linear board but also use siloed 'stacked' tasks and migrate them into a workflow when required.
If you're using something like SalesTrekker there's obviously no need to consider Planner " simply use a dedicated worklow for planning your marketing efforts. If you're using SalesTrekker but don't require the ApplyOnline functionality, Planner is often a suitable Kanban alternative. While Planner doesn't include all the same features as ST, certain Yabber subscribers will have access to our Yabber backend that provides integration for lead management, tasks, trigger notifications, checklists, and so on.
Yabber, our digital marketing and social system, is heavily integrated with Microsoft across a large number of modules. For example, we provide full Planner integration, include various task features, we fully support calendars (and we're the only company in the finance space to do so), and we've built a next-generation social media scheduling and sharing platform into a dedicated Outlook calendar. We're also just about to release an email module that records email attachments into a user table and optionally sends them to ST.