There is no definitive answer to this question. It ultimately depends on personal preference and what resources are available. Some people prefer to do recovery rides indoors because they have access to a trainer or stationary bike. This can be a more controlled environment where you can better monitor your effort and keep a consistent pace. Others prefer to do recovery rides outdoors because they find it more enjoyable and motivating. Fresh air and scenery can help to make the rides feel less monotonous. Ultimately, the best option is whatever will help you stick to your recovery plan and make the most progress.