Depends on the brand, in terms of performance and what you'll get.
My rough rule of thumb is that you'll get roughly half of the performance from a gaming laptop's graphics card compared to a desktop with the 'same' card. For example, there are gaming laptops out there with 3080's, but they're only going to perform at half of what a desktop with similar specs would with a 3080. The general reason for performance drops is because the laptop cards can cut down on other components due to space/power restrictions, as well as the laptops throttling for power saving and heat management. Long-term sessions can be even worse for laptops, as thermals will potentially throttle the entire system even more... which is something desktops generally don't have to worry about beyond extreme rigs. In essence, you'll likely get much better results with a 3060/70 desktop rig than you would with a laptop 3080 considering the specs of the current cards.
When perusing reviews and sales pitches for gaming laptops, you have to be very careful as they may be only telling part of the truth. For instance, it's not uncommon that you see claims of gaming laptops only apply to high power states, but said states may only last 40-60 seconds or so until throttling occurs either due to thermals or restrictions on the system allowing said state to only last so long. While such limitations exist in desktops, they can be overridden or are less restrictive since there's much lower risk of damage, whereas there's much less wiggle room for laptops.
If you aren't going to play games that are resource hogs or at cutting-edge graphical settings, gaming laptops can be a stop-gap measure until you get a desktop (especially if you travel a lot). Portability always comes at a cost, whether it's performance or the increased price tag. Overall, gaming laptops are getting better, but that also means that desktops are getting better. I still have a gaming laptop for when I travel, and it still performs fairly well... but I've also had to change the graphics card three times because of thermal damage despite my best efforts to cool the damn thing (and that isn't cheap!).