I'm not sure what you mean by bench tuning but the process of tuning is no different with ECUtek versus Cobb or Open Source.
Both ECUtek and Cobb are a complete proprietary rewrite of the stock ECU but both have their own proprietary hardware to interface with the ECU to perform read/write and logging and real time functions. Though ECUtek does not do real time tuning yet. Cobb only requires the purchase of the AccessPort and licensing for the downloadable maps are implied and AccessTuner race can be gotten after you pay for a training course. ECUteck requires the purchase of their dongle but I am not sure if that also comes with the license for the map. I think that is separate. I am also not sure about the tuning software but I think you have to pay for that as well.
Open Source is a ROM editor that reads and rewrites the stock ROM with the new changes that you make. In cases like the CarBerry ROM and other applied patches, you can almost consider it a complete proprietary rewrite of the ECU but I don't know enough about that to know for sure. It requires a Tactrix OpenPort 2.0
In the real world it almost doesn't matter so pick you poison. I just go with the cheapest option because they are all good.