I don't really find one to be better than the other, just different. I greatly enjoy both parks and each has great things going for it. I think both are moving in a good direction as well.
Cedar Point spent a long time with the focus being mostly on what new ride they were going to build next. In the last few years they have worked hard on some of the other things that make for a more complete experience. They have completely replaced some of the dining buildings and filled out the available food options with large scale offerings with Italian food and barbecue, along with the frontier festival. Is it the best food in the world? Of course not. But there has been a focus on better quality and high volume to help with some of the lines they've had in the past. The replacing of the front gate, marina gate, and resort gate, along with parking entry plaza all improve the aesthetic and guest experience. Much work has been done to the resort offerings, with all new and renovated rooms at Breakers and Express, new premium RV spots at Lighthouse Point, and the purchase of Sawmill Creek. They've added the Forbidden Frontier to provide a new interactive experience. Replacing the splash pad with brick pavers is an improvement, and is something I imagine we might see more of, considering they did the Valravn area with pavers as well.
Kings Island is doing many projects of the same nature. The installation of pavers along International Street is a great improvement in apperance and perceived quality. The parking entrance looks fresh and clean. The Area 72 redo looks fantastic with updated theming and sprucing up of the area around Orion. Bringing back the antique cars with a beautiful new installation was a slam dunk. Including the similar high volume barbecue restaurant that CF is adding at various parks was a no brainer. With Cedar Fair already redoing entrance plazas at some of the parks, I think it's just a matter of time before KI gets that treatment as well. Whether it's a refresh, or a replacement it will be a LARGE project.
Both of these parks (and Cedar Fair as a whole) have been focusing on the overall guest experience lately, and I think it has been a fantastic strategy. There is just so much more of Cedar Point to address. It's been around for so long and has some great challenges as far as these types of improvement go. The traffic patterns are more restrictive and with the volume of guests, almost have to have the "concrete jungle" aspect to an extent, just to accommodate the crowds certain times of the year. KI has the benefit of an initial plan more recently, on more of a blank slate. This sounds like an apology letter for CP, but it's really just something I notice when I'm at these parks. They are 2 entirely different animals.
I love them both though, and they are my most frequently visited parks in the last 5 years or so, along with Worlds of Fun. I made the drive from St. Louis to each park twice this year. And I can't say that I really enjoy one more than the other. If anything, KI has pulled up close to CP for me. And I think it's more because it offers something a little different, and its probably just as much me getting a little older and appreciating the differences and not just looking entirely at the coaster lineup(both of which are top notch, with CP taking the cake). Its a long day, but I can drive to KI, have a great day, and make it back home in one shot. At CP, it's obviously more of a 2 or 3 day thing. I love both experiences; it really just matters which one you want.