I've only ever used Addi circs in single sizes, but I liked them. I personally think Hiya Hiyas are a better value, at least as far as the single length circs go. I have several of them and love 'em.
That said, I notice a clever marketing ploy Hiya Hiya uses in their interchangeable sets. They have 2 sets, large and small, which go from... 2-8 and 9-15 (I think). The marketing trick is that the cables won't swap between the large and small sets. So for someone like me, who rarely uses anything smaller than a US 6, I'm going to wind up either buying stuff I'll rarely or never use, OR spending just as much to get the individual tips and cables for sizes 6-8. And on top of that, they don't include the cable for a 16" length in the set -- 18" is as short as you can go. I'm sure if you asked them, they'd say that even with the 4" tips they'd be too long for a 16" needle. (The tips are available in 4" and 5" lengths, and those DO interchange -- within the same set.)
All of that has me looking at the Knitter's Pride Dreamz interchangeable sets which go from... 4-11 and 13-17 (I think?). I have a couple of single length Dreamz and like them well enough, and my girlfriend has both interchangeable sets and LOVES them.