Re: They're playing to the dummies in the market...
Personally I'd much rather have a portable laptop (Samsung laptop or similar) than a pure ~10" tablet. But your argument does seem contradictory - you say this Samsung has no point, as it'll get slayed by laptops on every technical score, but ipads are fast enough to do what is asked of them? Which is it? Is something okay as long as it's fast enough, or not if it'll get beaten on specs by a laptop?
The weight difference isn't that huge - some people were evidently happy with 600-700g 10" tablets for years (including ipads), whilst the lightest laptops are around 1Kg (I think the lightest is a Sony just under 1Kg; ASUS's T100 is just over 1Kg). This Samsung tablet at 750g is still much closer to those tablets. Furthermore, 12" laptops are going to be heavier still.
You can argue in favour or against the larger tablets vs laptops, but I don't think this Samsung device makes a difference to that argument - any advantage or weakness or weight or specs is shared by the other tablets.
"OTOH going smaller doesn't achieve much"
I disagree - I intentionally didn't get a permanent case for my Nexus 7 for that reason, and the time when weight is most important is when it's in my hands. So having under 300g for a tablet that's meant to be hand held device is important in my opinion, and much lighter than any ipad heavy or other large tablet. It also means I can hold one handed, and use with my other hand - meaning it's easy to use without a desk, laying it on my lap, and I can easily use it standing.
When it's in my bag, the weight is of little relevance, I don't notice it any more than I notice my Samsung netbook in my bag. But the size is important - I can slip it into a side pocket of a bag, it takes up that much less space, and I can even put it in a small bag or even my pocket (just about!) which would be impossible for larger tablets.