The fifth is a 23 replacement. Haven't really used it yet. Probably slightly sharper, because 23 is generally flat in the lower registers. The partials get so small as you go higher, so alternate fingerings up there are pointless.
Little known fact: Before there were valved brass instruments, trumpet parts were played with trumpets in the range of tubas. They played them so high, however, that the partials were close enough to be able to play scales. They were also incredibly difficult to play.