It depends on the job, and your scope. If you are onsite-onsite, then big screen is a must. If you’re onsite-hotel, then I’d go with a bit more portable, and have an extra screen with you. Here’s mine (pretty light, portable, and doesn’t take much for teardown/buildup, price is right too):
https://www.amazon.com/AOC-U2879VF-Monitor-3840x2160-FreeSync/dp/B0163JLIWU
You should probably look into a cracking rig if you’re serious about providing that service. And not all customers like the “I’ll crack your hashes in the cloud” approach, so services might work for some, but best to have your own hardware you can vpn into off-site. Even a simple desktop with a single 1060 will out perform most laptops.
With those taken care of, it makes the laptop much more about personal preference and ergonomics. Good keyboard, a touchpad with working shutoff, available ports and layout, etc… And that opens up a lot more possibilities too.