Over the years, Cactus Game Design has used different printing companies, which has resulted in card sizes having a bit of variance. Having been involved in some of the discussions regarding print runs, I can say that Rob has always tried his best to find the highest quality printing source for the capital he is able to invest in keeping Redemption going.
I believe the Priests expansion was the first to use a different printer and it is very easy to distinguish one of those cards both by touch and look. The TexP set was a foil set and often the cards have a bend to them so those cards are also easily distinguished from non-foil cards. The first printing of the I/J starter decks was actually mis-sized due to an error by the printing company, but rather than waste all those cards, Rob went ahead and used them (after informing the community that they would be undersized).
As a result, the decision was made many years ago to require that all decks being sleeved for tournament play. Obviously that's not a requirement for pick-up games at home, but it is an easy way to avoid the issue of mis-matching card sizes. Hope that helps.
