HubSpot CRM is actually a different product than HubSpot. It's a little confusing because most people who are using HubSpot's other products (Marketing, Sales or Service) will be using the CRM, but you can also use HubSpot CRM for free, without the other products.
With Zapier, if you're working with anything that you'd primarily use the CRM for (eg contacts, companies, etc), then it's best to use the HubSpot CRM integration. If you're working more with content, then HubSpot is going to be the one that you need. There is some overlap between the two integrations in terms of what they can do, but that's the rule of thumb 😊