reasons to use postgreSQL rather than MS SQL Server Express

Our company has a project to migrate some financial
software from a Microsoft Access 97 database. This
software is run at various office locations, and each
location will require data-porting as part of the
upgrade process. Each databse is quite small, ranging
from only 10MB in smaller branches to about 600MB in
the gargest, with a typical size being arround 150MB.
The taget platform will be Windows 2000. The
application is written in Visual Basic (VB6), but is
likeley to be rewritten at some point *after* the
database convesrion.

The main requirements are:

* Low Cost
* Stability
* An installation and data porting process that can be
austomated
* Access from VB6 (probably ODBC)
* Accessability from yet unspecified "supported"
language for future rewrite (VB .NET, Java or C# are
good candidates at the moment)
* Some means for support staff to view and query table
contents

The obvious solution seems to be to migrate the
database to MS SQL Server Express. This seems to be
targeted to avoid small applications like ours going
to open-source. It gives the advantage of an easy
upgrade-path from ACCESS. The databases can be viewed
by support staff using ACCESS 2002, which has the
advantage of having a small lurning-curve from access
97. We are way below the limits currently imposed on
the Express edition, and it is not conceivable that
the data would increase to anywhere even close to the
4GB limit even in the long term.

I do have worries about Microsoft changing the "free"
licensing or reducing the limits in future releases.
Having succesfully used open source products in our
ecommerce system, however, I would like to consider
open source alternatives. I think I would need more
reasons not to use SQL Sever Express to convince the
IT manager that this is the best option; at the moment
I could only put postgreSQL as a "possible alternative
option".

Is there anything else I can add to strnegthen the
argument?Our company has a project to migrate some
financial software from a Microsoft Access 97
database. This software is run at various office
locations, and each location will require data-porting
as part of the upgrade process. Each database is quite
small, ranging from only 10MB in smaller branches to
about 600MB in the largest, with a typical size being
around 150MB. The target platform will be Windows
2000. The application is written in Visual Basic
(VB6), but is likely to be rewritten at some point
*after* the database conversion.

The main requirements are:

* Low Cost
* Stability
* An installation and data porting process that can be
automated
* Access from VB6 (probably ODBC)
* Accessibility from yet unspecified "supported"
language for future rewrite (VB .NET, Java or C# are
good candidates at the moment)
* Some means for support staff to view and query table
contents

The obvious solution seems to be to migrate the
database to MS SQL Server Express. This seems to be
targeted to avoid small applications like ours going
to open-source. It gives the advantage of an easy
upgrade-path from ACCESS. The databases can be viewed
by support staff using ACCESS 2002, which has the
advantage of having a small learning-curve from access
97. We are way below the limits currently imposed on
the Express edition, and it is not conceivable that
the data would increase to anywhere even close to the
4GB limit even in the long term.

I do have worries about Microsoft changing the "free"
licensing or reducing the limits in future releases.
Having successfully used open source products in our
ecommerce system, however, I would like to consider
open source alternatives. I think I would need more
reasons not to use SQL Sever Express to convince the
IT manager that this is the best option; at the moment
I could only put postgreSQL as a "possible alternative
option".

Is there anything else I can add to strengthen the argument?