I can't speak for the Slingshot boards, but I'll talk all day about Ronix. Before I go on about the 2014 boards, have you seen the 2015 stuff yet? Because the shapes changed for the One series. Parks and Bandwagon stayed the same.
Alright so first off you've got to decide whether you like a fast board or a slower board, a more aggressive edge or a smoother edge, abrupt pop or more abrupt pop, flex or no flex, and finally cost/color.
One series is going to have good speed with smooth, mellow edge to edge transfer with an abrupt pop off the wake. They're designed to be quick cutting but still smooth and under control. Time Bomb is going to be the most agressive, stiff One board, followed by the ATR and then the Modello comes in as the softest board. Basically you sacrifice some pop and weight for cost.
Parks is going to be the faster of the two camber boards, which isn't saying much if you're coming off of most other boards. It's got aggressive edges that will take you into the wake fast and once you learn to ride camber, will boot you. It's definitely a whole new feel. Air Core vs Modello is just the cores of the boards, although the Modello doesn't have a grind base. Air Core is going to be much stiffer and lighter, but will pop harder than the Modello will, which at a beginner/intermediate level you may not necessarily need.
Bandwagon, the slower and smoother of the camber boards, isn't necessarily a toned down Parks, but it's not as aggressive. I describe it as more of a surfy feel as far as cuts go. It's very smooth, but doesn't charge as hard as the Parks. I personally ride the ATR version which I love because I split time between boat and cable. Again just like the Parks, there is an Air Core version that is stiffer and lighter with a harder pop than the ATR. If you go the way of camber, you're going to have to re-learn to wakeboard. I'm an advanced rider and it took 2-3 weeks of riding for me to get comfortable on it, but once I did I love the way it pops off the wake. You can't ride tail heavy anymore, I ride with my weight centered 50/50 and popping off the wake is like doing a standing squat and jump on flat ground. It's certainly not for everyone.
As always stated in board recommendation threads: Demo demo demo. As much as you can. Most shops will knock the demo fee off the final price of a board if you decide to buy it, so it can never hurt to try boards and find out what you do and don't like, then look for similar traits in other boards that you might not be able to demo.