The cells in the right column of the table shown in figure 4.5 have different leading or padding. Observe that the default leading of the content of a cell in text mode is equal to the font size. Internally, the leading is set like this: This is different from the default leading of a Phrase object outside a PdfPCell.
There can be a lot of differences between a UDF and stored procedure, as the prior link has shown. Another difference is the UDF can be directly selected from, whereas a stored procedure requires one to insert the results into a tempory table or table variable.
One of the main benefits of using the Stored procedure is that it reduces the amount of information sent to the database server. It can become a more important benefit when the bandwidth of the network is less.