I think the "best one"(reference) I have is ADT7420, eval board from ADI. This one was below 10€, you can get it also on Ebay, but more expensive and unknown IC origin (why was it put on ebay, maybe it failed some spec?). But early tests show, that many different sensors are VERY comparable, some from Ebay, some bought from trusted seller, samples from manufacturers,...
Maybe you or someone else knows of some other sensors, that would compete or are even better
But it's not that easy to compare on gateway, I can't change it to the point, that I would have all graphs at once or see only delta from reference sensor