i havent listened to the mono collection and i have had it for years, at least it made it into my cave. the stereo mixes are strange, with extreme panning or unusual balances - i bet the mono sounds better.
It definitely sounds better with the earlier albums, but that's to be expected. Around Sgt. Pepper I thought stereo sounds better 'cause it's easier to hear the bass and drums. No wonder people failed to appreciate Ringo's genius; he was drowned out in the mix!