I guess for discussion if you want a data logger what data is important to you? The main things I want to see are drive shaft RPM engine RPM, 02 sensors, oil pressure, fuel pressure, Exhaust temps are old school but can be valuable info. Next is the sampling rate, the higher the rate the higher the cost. And as mentioned in other posts the software that interprets the data. How friendly it is displayed so you can use and understand it.