interbase v postgresql

I have an application on MSSQL and am wanting rewrite it using open
source software.

What would people here consider the strengths and weaknesses of these
two?

The things I need are:

Salability to hundreds of concurrent users.

Stored procedures. This seems to rule out mySQL. Which product has the
fullest procedure language?

I want two types of interface. Access via a browser or via client
software applications.

For web based access, I envisage using perl. Which product has the
most stable modules to connect to perl?

My client apps are written in Delphi. Although I've yet to get serious
with it, I think I can use IB objects to produce thin-client delphi
apps talking to Interbase, needing little to be installed on the
client machines. With postgresql I think I have to use ODBC. Any
reasons why one is better than the other?

For clients connecting across the Internet, traffic would have to be
encrypted. Could I achieve this with either product?

With MSSQL I really like the Trace utility. I can watch the SQL
commands as they arrive at the server. I understand from an earlier
post that this isn't possible with Interbase/Firebird. Can I do that
with postgresql?

Does anyone have opinions on this?
There is a bit of information on the project itself at www.openi.org.

regards
Richard

also posted to borland.public.interbase.general
richard(at)tortoise(dot)demon(dot)co(dot)uk