Also, open Image Capture and see if either scanner shows up in the "Devices" list. My Brother MFC was and the software is much better than the third-party trash they send with the printer/scanner/copier. But there could also be features that are not in the Image Capture app.
And it comes with your OS, so you've already paid for it.
As for not 'seeing any difference' between the old and new Leopard, you shouldn't expect to. Probably 90% of the changes are 'under the bonnet' as you would say!
But they are there and most of them simply make the OS more stable. But, if your machine is capable of using 64-bit apps, you may see an improvement in some apps, more when developers start taking advantage of that. Most of Apple's apps (including Finder) now run in 64-bit mode, but have 32-bit capabilities for older machines, also.
Of course, one thing that
is visible, is the new Image Capture app. Much improved, IMHO.