I could be wrong but I believe they can both (the 600 at least, I'm fairly certain), CAN accept 1080p... just obviously, not natively as the resolution isn't high enough. But I think it can accept the signal. So in theory, the TV would be downscaling the, in theory, if it's done right, best picture possible. Which ain't no bad thing!
They are both 1080i max input.
The differences are mainly that the sound system is apparently better and there is an SD card slot which will record and play lowish quality video. The display also has slightly enhanced software to provide subjectively better quality.
I decided these addons weren't worth the extra cost for the 600.
From memory, the Bravia smearing effect can be fixed by turning off something in one of the menus, though the 26" S-series apparently uses an 'inferior' panel to the 32" model.
Does anyone know whether the TX26LXD60 will be replaced anytime soon? It has been in the shops almost a year which these days seems a long time for any LCD TV
(Please Panasonic give any LXD60 replacement a PC VGA input, but there again it could be an excuse to save for an LXD600 or wait for the Sony U2500 series which will have 2xHDMI and should be available in a 26" size.)