this is one of the political intrigues of skyrim. through we can't really join either side, i would side with markarth because the forsworn is anti-empire. but there is corruption in markarth. so......

You're a little late, someone made this thread over in Skyrim Gen.

http://www.gamesas.com/topic/1498153-markarth-vs-forsworn/?fromsearch=1

Yup, in this one we can have a proper discussion because we're allowed spoilers and also I totally didn't jump the gun

I'm a Markarth supporter, but for the purposes of getting a discussion going I'm going to reply to the OP:

The corrupt elements of Markarth support the Forsworn and encourage them, it's hard to differentiate between the two.