My verdict is in: Despite the similarity of star ratings, Christmas Through the Decades is the better of his Christmas collecting books I've read.
In Christmas Past Brenner would not often make it clear what exactly were the differences between a style of ornament manufactured in Germany vs Japan, or more often, how they changed over the decades. To be clear, he still doesn't spell it out clearly, but this book is furnished with more (and (mostly) better) photographs and everything is divided by decade. A reader can decide for themselves about a particular ornament by going through the chapters themselves and looking at the images.
A problem is that the text is absurdly small and at least one paragraph is cut off in mid sentence never to be completed (about wax ornaments of the 1950s). The organization by time means that side by side comparisons can't be made on the same page, and his descriptions can still seem to contradict each other. Some of the text is directly lifted from Christmas Past (and likely, though I haven't read it Christmas Revisited), but the photographs are a boon for up and coming collectors such as myself who've had a hard time finding accurate sources. Brenner has done a great job with his research, and though other discoveries may have been made this may be the best general guide available to collectors (at least in the secondary market).