Hi @Helmut_Ritter, the good news here is that Roboflow makes it easy to test different approaches!
Just check out the Resize preprocessing step when you are creating a new Version. You can then experiment between two different models (using Tags and the Filter by Tag preprocessing step). These steps will allow you to train models on a subset of your data - you just need to tag the 300x200 and the 200x300 images accordingly.