The running score of GTX780M is higher than that of desktop GTX660, but much lower than that of GTX660Ti. Some critics point out that it is quite close to AMD's HD7870, and the performance of GTX760 is a little worse than that of GTX660Ti (really little). It should be that the performance of GTX760 & gtGTX780M & gtGTX 760m and GTX 760m is between GTX650 and GTX650Ti (biased towards 650Ti). To say cost-effective, of course, it is cost-effective to equip the desktop with a GTX760, and it is also convenient to upgrade the desktop graphics card. Just buy a new one and replace it. Notebook graphics cards are much more troublesome. Not only can high-end notebooks replace graphics cards, but this card is not cheap at all. I'm completely sorry about this price, and I have to mix with the maintenance department.
According to your situation, I think you have two choices.
The first one is what you mentioned above. You can buy any notebook and get a desktop. I agree with this idea, but I suggest that you can buy a notebook at will. Now that you have a powerful desktop host, there is no need to buy a notebook that is still expensive but has no performance. GTX760M is a chicken rib at this time. The money saved can be used to strengthen the desktop host, such as upgrading the graphics card to GTX770. In this case, it is recommended to buy some trendy and light notebooks. For example, Lenovo yoga 13-ifi can be used as a notebook, tablet and all-in-one machine. This is trendy, and you can also buy an ordinary Acer/Hewlett-Packard/Dell. It's true.
The second option is to buy ailenware M 18X with GTX780M sli, which is much better than GTX760. Evaluation shows that GTX780M Sli is better than the desktop version of HD 7970GHz on i7 4800MQ platform, or you can understand it as a super public version of desktop GTX680. Although the cost performance is not high, you bought this computer.