I meant, and should have said, that when all other things are equivalent (age, condition, subject, etc), the bigger the more valuable. I was comparing 1870s to 1870s, not 1870s to all other eras. It's true that baseball cabinet cards are relatively plentiful, but over 90% of them are from after the 1870s. In the 1860s to 1870s, CDVs were more common overall as a form of photography.
I originally was going to say 'all other things equivalent,' but assumed people wouldn't think I was saying that size is the only quality that matters. Clearly, an 1860s CDV of James Creighton will be worth more than a 1890s cabinet card of an anonymous barn, and a 1920s 3x2" snapshot of Babe Ruth will be worth more than an 8x10" digital photo of my dog. But the same Ruth or Creighton photo except in 8x10" form will be more valuable than the smaller versions.
And I know valuation bets can be off with baseball card collectors, as they sometimes prefer items that most resemble a baseball card. But I try not to submit to irrational points of view, such as with baseball card collectors who pay $1,000 for a $50 cut signature (with 3 of the player's letters cut off) just because it's on a Upper Deck baseball card with '1/1' stamped in corner
Hell, some card collector paid $600 for a scissors cut out magazine picture of Nolan Ryan, just because it was in a PSA holder and listed the PSA set registry. My valuation calculations don't include prices paid out by the insane, because they might start taking their medication or run out of money. Any good statistician knows you can't base your longterm valuation tables on the manic phases of the bipolar and those not legally allowed sign a contract.
Besides, I was claiming Leon's photo was even better when I found out it was bigger. I wasn't putting down anything.