Yes, you can perform an upgrade using the DVD media.
Usually I only do that when I have a mirrored disk but it's not a requisite.
Or you can use Live Upgrade, it's simpler however you'll need an additional disk in order to store the boot environment.
Quote:
And is downloading the latest recommended patch cluster just as good as upgrading to the next update?
Most patch clusters only fix the things that are currently present on the server. They do not add new features to the OS.
Personally I don't see a lot of "breathtaking" features on U10. Here's the full list:
Oracle Solaris 10 8/11 What's New - Oracle Solaris 10 8/11 What's New
I've always missed a native chroot option, though.