I really don't have an opinion to give you on which one to buy. I'm telling you what I would do. I would go with the TXS uppipe because I have heard more opinions/good things about it versus the scoobysport. Not saying the scoobysport is bad, just saying I haven't really heard anything (good or bad) about it.
Orbit and Deranged,
Again I don't really have an opinion/experience on flex pipes. But when I asked around about them when I was looking at uppipes, I had people saying the flex section would wear out after a while due to the heat and vibration. Personally, I have a Perrin, and I haven't had a problem with it yet. As for the sensor, it's really personal preference. As long as you know what you are doing and have the right monitoring equipment, I don't think that sensor is necessary. But Vishnu does make very good quality parts. Little expensive, but good.
Hope this helps you guys a little bit.