If you want to run ML tasks, a 4090 will smoke any laptop plain and simple.
You get to decide about convenience of having a laptop. I wouldn’t want to deal with the inconvenience of a non-nvidia stack.
That allows for some training to be slow but at least possible. When you look at benchmarks the memory can make a difference especially for LLMs:
https://www.reddit.com/r/LocalLLaMA/comments/16o4ka8/running...