Choice between a codeunit webservice or a page webservice

Hello all,

I need to implement a webservice to get information from one or several tables or to create records in one table.

I have already done this by publishing a codeunit as a webservice.
In this codeuit, there are several functions.
Each function has one or more input parameters and an xmlport as output parameter (ticked "var");

It works well.

But I would like to know what is the difference if I publish a page as a webservice ?
In which case is it more relevant ?
Is there any performance difference ?
are codeunit more relevant if we have to address several tables in one shot (although we could also create also a listpart page)

thanks a lot for your answer

Best regards
M. Bultel