Both great speakers , however I don't think you could pick two speakers that are more different.
I don't get hung up on what's HiFi , LoFi.... that's all someone else's opinion.
I haven't heard a Magnepan in a long time. I would imagine the 20.7 gives state of the art sound, or at least a taste of it. I have heard Cornwall and other big Klipsch many times and that's the sound I lean toward...
The smartest thing you can do when researching speakers is go out and listen to them. Especially at those,price points, but any speaker really. I just bought a pair of speakers sight unseen but they have a demo period.
There's no wrong or right, only what your ears and brain tells you. I have been to shows with treated rooms containing $$$$ gear that didn't wow me. I have heard modest systems that made me do a double take.