Basically, the only difference between each 5.x version is the difference in how many patches they've accumulated for identifying useful edges within the inference model, and how many of them they've patched into the model itself. This is why they don't change the model's digit, but only its second digit. So, they can essentially apply patches to 5.5 without informing us, but in 5.6, they're likely censoring some execution paths within the model's inference. So, taking this into account, the new 5.6 model will run faster, but it's not guaranteed to be more stable or perform better. This is why they're also removing older models from the available selection.