Hi
Choosing a vendor is a very critical decision when we talk about hadoop ecosytem. It goes by usecase by usecase approach.
HortonWorks provides only opensource components as part of their distributions but cloudera provides their own components such as Impala ,Cloudera Manager, Cloudera Search and many more. Not that HowrtonWorks doesnot provide, they provide opensource components. EvenThough Impala is openSource,it s not part of HDP.HortonWorks is betting on Apache Tez.So i would suggest to choose the distribution based on your client's requirements.
One more vendor to be noted is MapR distribution especially M7.It has its own positives.
You can refer the forrester report for the same.
Disclaimer: Opinions are solely mine and I am not inclined to any Vendor.
Thanks
Senthil Kumar A