Aren't every songwriters songs derivative of their older material somewhat? Nobody ever said "Golden Years" was derivative for being in the same vein as "Young Americans." And AC/DC don't really get too much slack for having an entire catalog of songs that sound pretty similar to all the other ones. I don't think "Straight Back" sounds anything like "SOTM" besides the fact that they're both in the key of A.
To be honest I think "Gypsy" was a major attempt at another "Dreams." The feel of each song is extremely similar, and have identical drum beats and the exact same kind of bassline, although with different notes (Doom, duh-doom, Dooom, duh doom etc.) That doesn't make the song any less enjoyable though.
To be honest I think the studio vocals of "Straight Back" are way more explosive than on "SOTM." Even though that's a great song she doesn't really cut loose like she does on "Straight Back." In the studio version of "SOTM" I always find myself wishing that the vocals were a little more wild and projected more.