From a sonic standpoint, you won't hear a diff.
From a feature standpoint, Sadie (like Sonic) being a dedicated mastering platform, gives you the ability right 'out of the box' to cut masters in virtually any format used by manufacturing plants: CDr, DDP (Exabyte or CDrom), & 1630.
Sampltiude can only cut audio CDrs out of the box, but you can optionally add DDP support (as I did), though 1630 is not an option.
Sequoia comes with DDP out of the box, but again, no 1630. The main diff right now between Samp and Sequoia is deeper/more flexible editin abilites in Seq as well as the ability to use the highly touted Algorythmix plugins. Samp and Seq will start to really grow apart in version 8 (for example, version 8 will no longer allow the addition of DDP support in Samp), so I am now looking at upgrading to Seq for that reason alone...