I have both. I think they sound fine together. I have the 210 on top. There is a subtle difference between the two.
What I like about having the 2 different cabs is the flexibility of choosing between the two cabs when I only need one. If I need both I'm good to go as well. I find myself using the 115 most of the time lately.
My recommendation is if you are really happy with the tone you are getting and just need more of it then go with the matching cabs. You know what you are going to get
If you are looking for a little more variety (again subtle but its there) go for the other. Buy from a place with a good return policy so if it its not your thing you can exchange it.
+1
My thoughts exactly. I have both and I think they sound AWESOME together! Totally modular rig. For smaller gigs, you have the option of whichever cab you might want to take that night, that's kind of cool I think.
I keep my 210 on top as well. Running both cabs (4 ohms) provides plenty of volume too. Plus they just look KILLER stacked!

