We do not have extensive experience with the larger “boxed drivers” like the TB6600 you mentioned, however the current handling of those drivers is noteworthy. The carrier boards for our most powerful stepper drivers (the AMIS-30543 and TB67S279FTG) can handle about 1.8A and 1.7A continuously, respectively. We do not know what the driver you mentioned can handle continuously, but we have the expectation that boxed drivers commonly can handle more current than that. Also, it seems like the I/O pins for larger boxed drivers generally work with a larger voltage range and have pins that work with inverted logic, which might save some hassle of using a logic level shifter or logic inverter if you are connecting to some controller with some fixed type of output. Also, those boxed drivers might have some kind of galvanic isolation (like an optoisolator) for the I/O pins. In general, those I/O differences are not likely to be an issue if you are using a microcontroller to control the stepper driver.
We do not have any long term reliability data for our drivers. If they are handled frequently, our bare PCBs are probably more exposed to ESD or mechanical damage. However, if our drivers are built into a system that uses the drivers within their specifications, we do not know of any reasons they should be less reliable.