Yes it does make a difference, honda 237. Different stores can and do purchase different wholesale supplier lot numbers of the same make, model and/or type of products, usually sold throughout the U.S. and as in this situation "Marineland Heaters and 1140 Powerheads".
As an example, Wal-Mart may get a different lot number which actually is a good working product, where PetCo or PetSmart may have a different and ineffective product of the same model, but with a different lot number.
I happen to own two 1140 powerheads which I have owned for 10 going on 11 years and they're still running strong without ill effect to any fish. Now, if the OP is experiencing issues with these two products with it's having adverse effects on his fish, it may be worth looking into. Especially if someone like myself may desire to purchase more of the same items proven to be worth their quality of manufacturing in the near or distant future.
My point being, if it's a defect, then it can be adressed by consumers to the manufacturer and greater attention to detail can be put into the QC of it's production, making it once again a lucrative and cost effective product for hobbists to use.
I hope this explains why I asked the question I did. Thank you for challenging my reason for the question. I do enjoy a good debate once in a while.

~David