Host client has been just recently introduced in vSphere 6. I would expect issues with it for some time until it becomes stable enough. For deployments with a vCenter, Web Client is the way to go. For non-vCenter deployment it would still be the C# client.
But that's just my two cents.
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VCIX-DCV, VCIX-NV, VCAP-CMA | vExpert '16, '17, '18
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