Hi ad-uk,
I have not used either of the two control panels you mentioned so i can't really comment.
Windows FTP + DNS = OK. The main problems with MS FTP & DNS though are that they are reasonably difficult to script, hence many look towards other solutions such as Bind for DNS and Serv-U FTP Server. In terms of performance, MS DNS Server can easily scale to many thousands of domains, plus we've been using it for years doing so. One minor point about MS DNS Server (many people will dissagree with me here🙁) is that Bind tends to get a lot of patches and bugfixes for security holes, whereas in my experience MS DNS Server doesn't get so many (unusual for an MS product i know).
Not sure if .Net server includes a mail server (assuming you mean POP3/IMAP and not just SMTP - Win2k has an SMTP server built into IIS as i am sure you are aware), and i can't really see M$ bundling one as that would probably devalue the revenue stream they've got in MS Exchange Server (not at all good for hosting).
Also for mail you could look at Imail from Ispwitch.com - we successfully run > 250k accounts on a single Quad Xeon with Imail. Some think it is a bit expensive, but i think it works really well for the price.
Hope that helps.
Cheers
