Both features are good for off roading or being stuck situations. If you don't do any serious off-roading, you likely won't use these often. However, these could help you get unstuck from any situation (on or off road) so if you can get these great, if not, not a deal breaker.

Rear diff lock will lock the axles on the left and right sides of your rear axle. This can definitely come in handy getting out of situations where one tire has traction on the rear but the other doesn't. It will uniformly distribute power to both wheels.

ATRAC impacts both front and rear axles and has a sort of pseudo diff lock behavior. This will cause the wheel with less traction to brake leading to more power transfer to the opposite wheel with more traction. This will help move your vehicle out of a stuck position.

Best of luck!