The verdict
Everyone with a website needs analytics, so Google Analytics comes first. It is free, and it works well for most small B2B teams, especially with Google Ads. Trackdesk is a later purchase, and only for a particular situation.
I'd pick Trackdesk when partners already bring in meaningful revenue and manual tracking has become a recurring headache. If you are still testing whether partners sell, a simple referral scheme or a lighter affiliate tool is enough, and Trackdesk is too much. Do not expect Google Analytics to do payout work, and do not expect Trackdesk to explain how visitors behave on your site.