As with so many things, it's the details that make a difference. It's what makes price shoppers different from value shoppers when prioritizing.
Blackstone is the Traeger of flat tops, decent enough quality, but heavy on marketing presence that makes it appear to be more than it is functionally. They are okay, and have been an easy way for many to get into using them. If you look at resale sites like FB marketplace or craigslist, whatever, you'll see lots of them for sale, often with rusted griddles and other deficiencies that result from abuse or neglect from casual users who bought on a whim.
None of that is to condemn them, and a conscientious user will get reasonable service from one. The most common complaints/concerns are the rear grease dump port, wind issues with the flame, uneven heating of the surface, and some of the "flimsy" concerns voiced above. Warping shows up regularly, but that and, to a degree, the uneven heating are user error or misunderstanding. Uneven heating is going to occur to a degree on all flat tops, and is actually a positive if understood and used as a cooking tool, if not too out of bounds. Warping is almost always user error, caused by starting from cold at too high of a heat setting instead of creeping up on surface temp.
My preference for a patio unit is the
Camp Chef. Made from slightly heavier gauge materials overall. The griddle surface is far better because of how it is reinforced on the backside. Most griddle manufacturers I'm aware of weld angle iron braces to the underside to add support/strength. CC has a large multilayer diffuser welded to the bottom that both functions as bracing and heat distribution unit. Once heated, it gives a better, more even heat zone, and with lower fuel use on longer cooking sessions because of heat retention. There is also a skirt welded on the underside that acts as a wind break that
Blackstone users who need one have to buy separately. There are some complaints about griddle top warping and the diffuser "popping" loose, but again, that's from improper usage, not design defect. The grease catch and drain is in the front which some think is a bad thing, but if you watch "pros" using a flat top they prefer it as they don't have to reach over to manage the going into a catch device that is unseen in use.
BTW, if you want to get some valuable tips on usage there's a YouTuber by the name "The Flat Top King" who has some good tutorial/info vids.......highly recommended.