Both types are equally common, but the primary type is always linked to renal artery stenosis. 

Primary hypertension has no specific cause and accounts for more than 95% of cases, while secondary hypertension is due to another disease and constitutes 2-5% of cases. 

Primary hypertension constitutes 2-5% of cases and usually resolves with treatment of an underlying disorder, while secondary hypertension has no identifiable cause. 

Primary hypertension is caused by pheochromocytoma, while secondary hypertension is environmental.

Secondary hypertension is idiopathic and more prevalent in black individuals than primary.