Actually I am not "Mr Chaudron", but an owner of a Chaudron boat. But I think I know about the 25 you are talking about, should be the red one with the 250xs Mercury. That is really a nice boat with good performance though the 250xs seems to perform no better than the 250 EFI.
the 250xs is an optimax engine (low emission) built by Mercury Racing and should burn less fuel than the EFI. But it requires 96 RON petrol to run unlike the EFI which can run on pump has. I heard that it made around 275hp but really does not seem to be the case. Seems to be a standard 250 in performance. The 300x however really buzz...a very powerful outboard