Well, of course, I can only tell you from the MySQL point of view - as you
expected. Just a few thoughts about it.
I must stress that
the most important factors are cost to the client, ease of self
installation, size of learning curve for us and the ease of future
enhancement development and support to the client.
The commercial license for MySQL, as far as I know (but please check it back
to be sure) costs about 500 dollars or 500 euros (I'm not sure, but the
difference is not that big ;-)) per server. That's probably something where
SQL server can't compete.
MySQL 5 (I highly recommand you to choose version 5, if you go for MySQL) is
very conform to the SQL:2003 standard, so whatever your developers have to
learn about MySQL does also apply in a high degree to other RDBMS. At least,
it won't be harder to learn MySQL from scratch than SQL server. For support,
take a look at
http://www.mysql.com/network/ - for 245 euros/server & year
you get support and a lot of additional services compared to the community
version (that most people use). I'm not sure, but maybe it even includes a
commercial license - if that's the case you'll certainly be better of with
MySQL Network.
Performance is definetly no problem with MySQL. It's of course important to
choose the correct database design, but this applies to any database system
;-). Just want to say, if you might hear critisism that MySQL offers bad
performance (maybe some hard core SQL Server freaks could come up with this
lousy argument) - that can only be a result of bad database design or an
incredible weak hardware equipment (in which cases all the other RDBMS also
would fail). Here's also an interesting link to read:
http://www.linux-mag.com/features/monty.html
Another argument for MySQL is that it's plattform independent. Should you
ever choose to use a Unix/Linux server (or most other operating systems),
you'll have no problem at all.
There's one argument for SQL Server (in comparison to MySQL) that comes to
my mind - SQL Server still has some features that MySQL doesn't have
(although much less since MySQL 5 is out). But I (my personal opinion - of
course you'd probably hear different opinions in a SQL server newsgroup ;-))
would say, unless you really absolutely need a feature that SQL Server
provides and you can't live without it or create a decent workaround, I
would choose MySQL rather than SQL Server. If you're missing an important
feature in MySQL, you could also check out PostgreSQL
(
http://www.postgresql.org), which is another very good Open Source database
server.
Markus