Modern Tally Ho decks are no longer made with Tally Ho card stock. At some point in Jarden's tenure running USPC, the stock was removed from the inventory. If forced to guess, I'd say it was after the original Propaganda deck, which was advertised as having Tally Ho stock.
Having said all that, modern Tally Ho decks use a modified version of Aristocrat stock. The Aristocrat reprints are noticeably softer than old AND new Tally Ho cards. By tweaking the moisture content, storage temperature and other factors, the stock can actually be tweaked to create variations. And Aristocrat stock is nothing to dismiss - it's generally considered casino grade.
I personally think the current-issue Tally Ho decks are actually very good cards, among my favorites. Decks made from 2011 forward are particularly better than those issued 2009 and 2010 - the infamous "shakedown" period of the new Erlanger facility. I couldn't compare them to older Tally Ho decks because I don't own any.