When it comes to exercising, what's better quality or quantity?

Basically, is it better to do let's say 1 hour of intense work out or 2 hours of not so intense?
I always thought and did the former but, recently this guy told me the latter gets better results. I don't see how that makes sense.
Quality
Quantity
Select gender and age to cast your vote:
When it comes to exercising, what's better quality or quantity?
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