Hmm, interesting question. I don't know much about Cobia. They were once long ago built in the next town over from where I grew up. I suspect they are a good quality boat. Every boat has its compromises.
I know Grady kind of over builds their boats. The deck hardware, lifting rings and such they don't go cheap. The LED lighting is top notch. Here is the thing. Do you buy stuff for your needs or do you buy stuff based on what complete stranger thinks your needs ought to be?
Back in 2009 I suspect I could have purchased a bigger boat, like 3 maybe 4 feet bigger than my 228 for what I paid for my 288 from another company, like Cobia. I didn't, because I wanted a Grady. Today because I keep her undercover my gelcoat is still shiny. I do wax her twice a year with collinites. There is not a rattle or shake in the boat . All the topside parts are in great shape. I have upgraded my lighting to LED tech. I have added stuff here and there. Would the Cobia still be nice? I suppose given the way I keep my current boat. I know this. One day I will likely sell my boat and it will command more money than other boats of similar size and age, including a Cobia. The market don't lie.
If you like the Cobia more and it meets your needs better than the Grady who is anyone going to tell you what is best for you? Buy the boat you want to buy.
If you are buying a boat to simply impress people like me, then buy the Grady. Otherwise , all the Grady owners in the super secret Great Great Grady Forum and Secret Society will be laughing at you. Lol. To be a part of that forum you have to have at least 30 feet of LOA and know the secret handshake.
I don't think you will necessarily go wrong with the Cobia.
Ask yourself this. Does the Cobia have the equivalent rod holders? Are you going to fish and sandbar it? Does the Cobia have the same high nickel stainless steel hardware as the Grady. Does it offer the same flotation? Grady's above 19 feet have basic flotation and if you are buying new they claim they are unsinkable. Does the boat have standard trim tabs? Does the Cobia offer similar or better customer service after the sale as Grady? I got some minor stuff covered after warranty expired. Grady makes access to their gas tanks easy with deck lids. So , you don't have to cut into the deck to remove the tank. Does Cobia offer the same thing? Does Cobia offer midship cleats? Does Cobia put two bilge pumps ,one with high water alarm in the boat? Lastly, does Cobia offer a bikini clad lady to come clean your boat for free? Well, neither does Grady but if they did, it would be double prizes for sure! Lol
I am trying to be funny, but pragmatic too. Get the boat that will meet your needs the best.