Both are very solid. The Sprints are a newer design and have a feature that I've come to appreciate that allows you to map curves to the pedals. They are both very configurable in terms of travel, position, pressure required. The Ultimate's are an older design and do not support the new software that allows you to map curves.
The Ultimate's main feature is if you need 300 lbs of pressure on the brakes to simulate a real race car. They also have hydraulic dampers, but I would highly recommend the Sprint Pedals unless you absolutely need very high pressure.
If it matters money wasn't an issue for me. I would have gotten the Ultimates if I thought there was more value in them. For me the software mapping the Sprints have was a key feature. However the Sprint pedals are also a newer design and are supposed to be EMI issue free, safe for transducers and designed with a very long lifespan.
Heusinkveld stands behind their products very well, so I almost wouldn't worry about any lifespan issue with their products, but my feeling was that the Sprint Pedals were more advanced and a better product. The Ultimate pedals need a refresh.