Well yeah I'd pick GH, cos Im more of an EC fan...BUT
I think about Radiohead this way; Pablo Honey was them as an Oxford indie band, starting out followwing the britpop trend...The Bends is a phenomenal album, them finding their true voice, but it's still an album which can be appreciated by the mainstream on the whole.
OK Computer was the record that many think defined them..it was the turning point for them creatively. The first time Greenwood (a great musician by anyone's standards) was allowed to have a free reign, and Yorke could fully instill his bile and disdain for modern society into the songs, but this record still has an element of mainstream in it.
Kid A and Amnesiac, although both OK, were rushed and diluted. These two albums put together, with some songs removed, would have been a masterpiece....but that came with Hail to the Thief. The album, creatively inspired by the political situation at the time (Hail to the thief was a banner held up when bush won presidency), and as such, the band got to let loose.
Anyway back to the question... if you think about OKC in those terms, as the turning point for the last BIG band (i.e. one that will be remembered forever for creating something new) then it is a masterstroke. I think in many ways Get Happy can be seen as such. This was the first album where he didn't try and live up to the 'angry young man' moniker...the first album where he covered old soul records, and experimented with other influences fully - a thing he would start to do on every subsequent record.
On strictly aesthetic terms I'd go for GH as a better record. In terms of which has the most emotional impact on me, it's OKC.
You can sing along with Gh though!!!!!! Try dancing around in your underpants to Fitter Happier!!!!!