I wouldn’t go back to Vray, for one reason, the internet licensing. I didn’t liked that i needed an internet connection for working with the software, every time i just start a test rendering.
And i think Cycles render quality is very good and comparable to Vray, others in this forum have shown that for me, for example that great pictures : The Broad House 
). The only thing i would like to test someday is Octane, but at the moment i am satisfied with Cycles. Hth.
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