There's been a few threads about the excellent LCW-M100Ds, and a few mentions of the LCW-M170TD, but I've not yet seen any threads dedicated to it, yet.
Same module as used in the LCW-M100Ds (as well as several other models), so tough solar, multiband 6. The LCW-M170 is available in stainless steel, as well as titanium (as are the LCW-M100s), and in some other colour derivatives not seen (I think) with the LCW-M100Ds (ie all black - not for me, personally, but I know some like them like that).
So ostensibly very similar to the LCW-M100D - visually very similar, same module, so same features, same water resistance rating (50m), also available with sapphire glass. The face is slightly bigger, and in general, it looks slightly more elegant / dressy. They've tried to reduced the impact of the "feature" writing on the face (ie "MULTI BAND 6" and "TOUGH SOLAR" is still there, but they've seemingly reduced the font size, slightly, and move some of it to look more subtle.
My only real bugbear with the LCW-M100Ds was the chapter ring looking rather cheap and plastic-y, they've very much improved the look of that on the LCW-M170.
As to the size, well personally I'm quite comfortable with modestly sized watches - the LCW-M100D was probably on the smaller size that most manly-men feel comfortable to wear, without being all self-conscious over whether it makes them look a bit girly. If you suffer from that affliction, the LCW-M170 is just that bit bigger, so you'll not have to feel you're not a real man, if you choose to wear one.
Here's some pics I took, comparing it to my JDM LCW-M100D (which in comparison, doesn't have sapphire glass). I do have a LCW-M100DSE-2AER with sapphire glass, but has the blue face and isn't on the stock bracelet, so I figured this one with a white face would be a more fitting comparison.
So this is a LCW-M170TD-7AER (titanium, sapphire glass) and a LCW-M100D-2AJF (stainless, not sapphire):-
I was very interested in this model when I'd first noticed it, although already having two LCW-M100Ds I wasn't that highly motivated to splurge on one. Have to say, though, now I've got one I really like it. I've often championed the LCW-M100D as something of a bargain as well as a sleeper, and I know the 170 is more expensive, but the only thing that irritated me about the 100 was that once you'd noticed how naff the chapter ring looked, it always niggled.
I'm delighted with it, titanium, sapphire, solar, atomic, and perfect second hand alignment.