I think the only thing that is the same or similar between the old HD LH and the new LHT, is the optics and the available reticles.
The new LHT has a 30mm main tube, illuminated reticle but I think only the center dot is illuminate not all of the reticle, exposed turret for elevation with a zero stop feature, and you can get one of the 3-15 models with a 50mm obj.
I have three Razor HD LH 3-15x42's on my small caliber rifles and they've been great little scopes, and that's coming from someone that isn't all that big a fan of Vortex. It'll be interesting to see if this new model is any better. I do like the idea of the exposed elevation turret though.