A/V Quality of UK discs vs US

[srinivas1015]

I have been buying BDs from the U.S till now and recently opted to buy a couple of discs from the U.K. I don't know if this is simply a placebo effect but I noticed the dialogue in Wall Street from the U.K to be a little muddy and the picture in The Hangover(U.K) to be a little soft.
Is this simply my imagination or has somebody else also faced this problem? Are the codecs/bitrates etc identical or do certain aspects differ from country to country?
Kindly help me out.