The verdict
For a small B2B team without Salesforce, I'd pick ActiveCampaign. It is easier to start with, it brings a CRM and you can change course later.
I'd pick Pardot when the company already pays for Salesforce, has enough lead volume to justify a dedicated platform and wants marketing and sales to use one set of records.
Pardot is sold on annual contracts and priced per organisation, not per user, so ask Salesforce what each edition includes and what an upgrade costs. If you are still deciding where your pipeline lives, look at HubSpot as the CRM-led option before you tie yourself to either.