what is the best laptop for 3D max ? and why

It all depends on your personal needs and your budget. For example, a newer i7 processor, a xeon processor, and a lot of ram 16Gb or 32Gb would be nice. Also good ssd of 512Gb as well as a good graphic card I personally prefer nvidia and the good battery to withstand some heavy rendering..There are a lot of offers on the market, but as I say, it depends a lot of your needs... like: Razer Blade Pro, Dell XPS9560, Acer Predator and so on...

As the guy up, it really depends of on what kind of project you're working on. I have an OMEN by HP i5, 6GB ram and a NVIDIA 960M GTX and it goes pretty well :)

Personally, I wouldn't go for a laptop if you can help it. Desktops will allow for much easier upgrading and overall will be worth more for the money you pay.

If laptops are your only option, then I suggest you make sure it had a very good battery, its own independent graphics card and at least an i5 processor or any of the new AMD Ryzen chips. Around 8GB+ RAM and an SSD for faster data transport overall. I'd imagine that would be in the region of about £500-£700 [$700-$900]