My friends and I were noting that it seems that coins from the Denver Mint are always more brilliant-looking than those from Philadelphia. Is it our imaginations? To us, it appears that the dies or the blanks used in Denver have a better polish. It's strange because collectors would feel that the blanks are made in a similar way. Even in the annual Uncirculated Sets, you can tell which set is the Denver without looking at the Mint Mark; just from the brilliance of the coin.
It's not unusal really, with few exceptions, the coins struck at the Denver mint in a given year are of a higher quality than those struck at Philadelphia.
Actually, unless something has changed, the dies are all made in Philly. I do believe the luster problem has something to do with the pre-wash or acid baths prior to striking if my memory serves me correctly. Philly seems to always have a "dirty" look but have notice their quality is improving from time to time.
Here's one of those modern exceptions...SAC dollars. Finding high graded SAC dollars from the Denver mint (MS68) are more rare than their Philadelphia counterpart. But then again, your 1971-D IKE is worth less than a 1971-P IKE in the MS65 grade. I guess it all goes to who is in charge of the quality control when the coins are struck.
All kidding aside, I do believe it comes down to the employees and if they are willing to give it their best effort every day. Denver usually has Phillie beat hands down, and from year after year.