Would probably go for NT.

NT can indeed handle databases of this size, however for the 32 bit version of Oracle, you must ensure the database is comprised of files <= 2Gb.

My reason for preferring NT is that there are plenty of users running oracle on NT. Many issues have been found and resolved. There isnt the same userbase (IMHO) for linux.

Now if you were to offer Unix vs. NT (say Intel Sparc?) I would certainly go for unix with a database of this size.

Good luck with whichever one you go for.