Just curious about this, for example Shotokan and Kyokushin karate, would it be a waste of time to train them both since a lot of the blocks and kata, etc are similar or will it be useful? How could they be used in unison? If I am missing some key differences (apart from training methods and type of sparring each do) please point them out. Also if you can think of any other martial arts examples/comparisons please say so.
What disadvantages would there be to it?