Hi,

There is currently no easy way of moving from one db platform to another. It is possible using some 3rd party tools like SqlYog to migrate using queries but its not trivial. Once upon a time some years ago I was running joeaudette.com using Rainbow portal and MS SQL and after I started the mojoPortal project I migrated from the Rainbow MS SQL schema into mojoPortal/MySql using SqlYog.

Eventually I or someone else will probably implement a migration/backup tool for export and import of data. 

I think both platforms are quite capable, typically the choice is based on personal preference or views on licensing. SQL Express is free and can scale up to 4 GB databases but beyond that you need an MS SQL license, but even with MySql if your scaling needs go up you may need the enterpsies version or some third party tools for replication etc, so the actual costs are hard to speculate on. If you have skills/expertise in one over the other that is also a reasonable way to make a choice in my opinion.

Best,

Joe

Yes, but there are some differences in data types, for example MS SQL has a uniqueidentifier data type for guids and in some dbs we are using char(36) or varchar(36), Some dbs may be using an int or tinyint where MS SQL has a bit data type.