I got photomatix first when I was exploring HDR...and then I caught the NIK stuff when the suite of that went on sale for like $135. I like them both...if I do some HDR shooting, I'll often see what looks I can get out of both of them.
+1 on that. I often prefer the HDR in Photomatix (though it is usually close), but the Nik tools are a tremendous investment. After processing a handful of images, it has become a go-to suite for me since I can retouch parts of landscape images very efficiently. Pro photographer Tony Sweet has a discount available on Photomatix; I think his discount for Nik is gone since they lowered their prices so much from the Google buyout. He has discounts for many other suites and tools as well, so check out his web site before buying.