Not a continuation of the previous 3rd party lenses vs original brand lenses.
Here's a fact sheet / report from Lensrentals.com, a rental site in the US if I'm not wrong.
And a commentary on Sigma lenses:
Seems like paying for the price of original / mainstream lenses are pretty worth it.
However, do understand that they are a lens rental company. That is, every time a customer wants a lens, it is shipped out, and then shipped back, so handling of lenses will vary a lot.