use subdomains with wordpress multisite?

Hi
I need to run two different subdomains with wordpress from a main website (each subdomain should have its own database, different plugins, shopping cart, they’re large inventories so I’d rather not have them mixing etc).

Also, I wouldn’t necessarily need the main website (www.artroot.com) to run wordpress as it’s basically just directing to the subdomains.

I never used multisite. Does this seem like the best option? – instead of two worpress installs on each subdomain?

The structure for the project is (let’s say):

http://www.artroot.com (this will be only a simple homepage that links to the two subdomains)
subdomain 1 would be http://www.artroot.com/artjournal
and subdomain 2 http://www.artroot.com/artprogram

Also, I’m building this locally first, so any recommendation about this (multisite or different wordpress installs) in relation to mamp would also be welcomed.

I could easily buy three webdomains (instead of using subdomains) but that doesn’t seem the best option – I’d like the visitor to google the main site not the others.

thanks!