The best marketing automation integration for Dynamics 365 depends on your business size and/or marketing automation use case.
Picking a marketing automation platform to go with Dynamics is a little less straightforward than picking one for the dog in the market: Salesforce. There are fewer good integrations to choose from.
Here’s my thoughts:
Small business / low usage. If you’re a small business or are just starting out with marketing automation, Dynamics now offers its own marketing automation platform. It’s still very basic, but it will allow you to build landing pages, emails, score leads and automate campaigns. The alternative here is ClickDimensions.
Note that both the Dynamics Marketing and Clickdimensions suites actually live in your Dynamics interface, so that’s a plus from a usability standpoint.
Medium business / medium usage. If you’re a little more advanced, you want more functionality under the hood. I recommend you look at either Act-On or Net-Results, both of which have plug-and-play integrations going for Dynamics 365. I’ve heard far less good things about integrations with comparable platforms, such as HubSpot or Pardot.
Enterprise / heavy usage. If you’re a larger company, or if you’re kicking butt with things like onmi-channel personalization, dynamic content and advanced segmentation and lead scoring, I can only think of Marketo (and if that’s where you’re at, I want to talk to you). While their integration isn’t as tight as that of Act-On or Net-Results, it’s a plug-and-play integration and the platform offers far more firepower for advanced users. Competitor Oracle Eloqua, as far as I know, doesn’t offer an out-of-the-box integration.
Hope that helps!