I don't have a laptop,
, but if did would opt for the top of line in performance (assuming I had the budget).
The choice between desktop and laptop comes down to:
1. cost: more bang for $ from desktop than laptop
2. performance: definitely more power from desktop
3. use, convenience and mobility requirements
The ideal is to have a good/best performing desktop for final rendering and a laptop to help with mobility and presentation to clients (although its not really much of an issue lugging a desktop to a client either
Have not heard of any situations where Lumion users have overheated their laptop causing a burn-out due to rendering. As most modern GPU's have temperature control and shutdown, any burn-out would be due to user not taking care with heat and ventilation issues of the laptop.
Expect though, for final highest quality renders, especially at 3Star with lights etc, for some renders to take overnight or longer, but render times can also be managed in Lumion through a number of choices about the scene.
M based cards have reduced performance to fit in to the power consumption specs of a laptop so a GTX780 is going to provide a lot more performance than a GTX780M. See the specs on NVIDIA, number of cores and bandwidth are much less for the M.
Whether that has any impact depends on the nature of Lumion scenes and the amount of final rendering required.
A GTX780M may have similar power to a desktop GTX770, well more like a GTX760, so it comes down to the mix as mentioned above.
See also other comments in topics: please search for laptop or NVIDIA etc, there are lots of topics although some are not in the guest forum section.
Please see: Passmark: Videocard Benchmarks
In any consideration of a PC/laptop, please give due consideration to our hardware guide on the forum at LUMION 3: Minimum hardware requirements
, and the official info on the Lumion web site - Specifications
Also, each new version (and updates) can sometimes provide more features that may have a cost of additional processing to run, for example the soon to be increase in Reflection Planes in Lumion 3.1.1. This means then that like all things, the more power you can get for the budget or if you can extend the budget now rather than in future, the better off you should generally be.
Does the 780M come with 4GB, as the 780 standard memory is only 3GB?