Blu-ray or Standard Def?

[fogenthedemon]

I'm at a loss here. I have read several reviews on different websites that are generally in agreement over the picture quality of certain Blu Ray titles. Lets just use "3:10 to Yuma" as an example. I've checked several reviews and they all seem to rate the picture quality on it between 4 and 41/2 out of 5. I head over to Amazon.com to read some consumer reviews and after flipping through page upon page of reviews of the SD edition I come across one or two reviews for the Blu Disc. These reviews claim that there is virtually no difference between the Blu Disc and an up-converted SD edition. Who's right here? I've been doing this for hours and I'm making no progress, is there a definitive Blu Ray review site out there? Are the nay sayers at Amazon the same type who decried DVD back in the day? A little help would be greatly appreciated as I'd rather not rent a Blu Disc and SD edition of every film I want to buy to make a comparison.