ZoomInfo Vs SalesIntel

Product Capability SalesIntel ZoomInfo
Integration
Marketo, HubSpot and others
Salesforce, Marketo, Hubspot
Intent
Sourced From Bombora
Do not know
Technographics
HG Insights
Acquired Datanyze
News
Owler
Press Releases, Syndicated Sources
New Hire
X
BeyondCode’s team
People Data
CircleBack
Connected to millions of Community subscribers

Leadership:

Manoj Ramnani is a very passionate and hard working CEO. SalesIntel is building a good sales team. I met him in December, 2019. Manoj has infectious enthusiasm and energy.
ZoomInfo has a very talented and senior leadership. Many of our clients come to us because 1. Their teams cannot make use of ZoomInfo 2. Results of the entire year’s worth of marketing using ZoomInfo did not give them much.
It is not easy to beat ZoomInfo with its history and vastness of sources that it has built over the years. OceanFrogs can do it because of its investment in research and data science.
In case ZoomInfo and SalesIntel do not satisfy your need, take a look at Oceanfrogs.

HGInsights Vs DemandMatrix

This one is a tough one because Meetul Shah is a friend. While we have not seen HGInsights data, we can confidently say that DemandMatrix is really good at what they do. Demandmatrix has been successful with many customers such as DocuSign and other large enterprise customers. Case Study on DocuSign is one of the most famous case studies that Mintigo built its reputation up on before being acquired by Anaplan in 2019. Case Study on Docusign using technographics was also one of the earliest victories of data driven marketing or predictive marketing as it was called back then.
HGInsights is known for its deep insights on technology data. SalesIntel uses them.

ZoomInfo Vs D & B

ZoomInfo has the brand image over D & B. This is our opinion based on what we hear in the market. Our customers are primarily focused on the USA market. Many of our clients use these two databases. These two are still treated as static databases. Customers want to go towards intent driven databases. 
Customers do not want to buy data from multiple sources and integrate them. ZoomInfo solves that problem to a good extent. ZoomInfo has become unaffordable for companies in India. ZoomInfo also insists on annual payments (and that is a good thing).
Take a look at G2Crowd reviews of this category.