external optical shaft encoders vs integrated encoder module

Out robot is running into size issues - getting beyond 18" in width (about 19.5 inches now on the front of the drivetrain base) if we add two external optical shaft encoders. So now I am thinking of rather replacing existing 393 motors with the internal encoder module. Are people using this - is this reliable? Would like to know suggestions before I start using these. Thanks!

In my opinion, encoders are much more reliable. The IMEs have tendencies to do weird things, so I would stay away from those. Of course, if it is impossible to fit in an optical shaft encoder into your design, then feel free to use an IME.

So are shaft encoders more reliable than integrated motor encoders? Because our team is making a decision between those two encoders.

Integrated motor encoders are known to cause issues with static discharge that can result in endlessly running motors and unresponsiveness to field control.

For this reason, shaft encoders are almost always better options.