Listen, but don't take anyones word as Gospel
So in my opinion there is not one specific answer. First do you have room for a bigger laser? 2nd, and in my case 2 lasers which are smaller work better for my situation. Twice as fast!
3rd. One of the reasons I have 2 laser is a just in case. I use both, but what if one goes down. At least I can still process orders while the other is being fixed. Even one day hurts me!
4th. Who do you plan selling to? If you plan on doing large items from the start then of course get a big laser.
5th. Every product I do right now fits in my smaller lasers. (27" x 18"). Until I find a need for a larger laser I would not use the extra space anyways. I am busy enough with what I am doing. If you find a need for a laser laser I may get one.
So you see every situation is different. But of course you don't always know what you will need until you need it.
Do a lot of research.
Redsail x700, 50watt & Shenhui 350, 50 watt