I remember reading that Continental 25s measured most closely to 28s.
I would tell you to go tubeless and forget about it as my Schwalbe One 23s are a great ride. You can get the tubeless in a 25 and sometimes a 28 also.
I know on my Orbea a 25 is as wide as I can run and the Continental 25s were a tighter fit than the Vittoria 25 I ran for a bit.