It all depends on what sort of functionality you need in your CRM.

There are a number of small ISOs that use Hubspot and it seems to work well for them. It's easy to use but lacks more advanced functionality so you may grow out of it pretty quickly.

I've used Salesforce for a number of years and it's by far my favorite. The reporting/analytics is great and the system as a whole is very customizable to your needs. With the customization may come headaches though, if you aren't familiar with Salesforce you may need help dialing it in.

I have some experience with Microsoft Dynamics as well. I do not recommend. It's very clunky, felt like it took 3-4x as long to do anything. Ended up switching to Salesforce.