They are different.
1000S has a faster UI but retains some annoying foibles like the daft order of displaying recordings in series folders. And of course it's restricted to recording two and watching a 3rd. My 1000S mysteriously rebooted about 9 mins into a recording of Corrie yesterday evening and dumped the recording. The 5000T came to the rescue.
The 5000T is slower to respond to the remote and the supplied remote is a tad weak. Not an issue for me as the 4000T device on my Harmony remote works just fine. And I sit very close to it as like my other kit is at the opposite end of my room to the TV in a HiFi rack.
You have more ways of displaying your recordings than you can shake a stick at
It's so far recorded everything I have asked it to.
Picture quality on both is excellent.
It can of course record up to 4 and watch a 5th subject to mux.
As all the 5 main HD channels are on the same mux, and I rarely record other channels that in practice it can record 4 of them and watch the remaining one live. You can also set a reminder on the 5th to ensure the beginning of the programme is within the time shift buffer and record that using instant recording when one of the other recording terminates.
This makes it a very flexible box so if you only want a single box and don't mind the slightly pedestrian UI it's a no brainer.
Also the software is very new so is likely to improve with future updates.
If they could add a series capability to reminder reservations and a auto record when the number of current recordings falls to 3 that would be pretty cool, the hardware is clearly capable of this.
Perhaps logitech might consider a timed remote command option
One slight annoyance is when you open a series folder, the newest is selected rather than the oldest, shouldn't be that hard to change this I would think.