Seriously both messed up stories about messed up characters and the same medical torture thing and human experimentation elements in the case of both the clones in Duel and in Taemin's arc. Traumatic backstories and more emphasis on the bromance. Final Life feels like a bad dream, very artistic, definitely a must watch.
While Duel is more suspense thriller, and IRY is more crime solving - what stood out for me was the heartbreaking bro-angst of two characters in both dramas. Without spoiling, you'll realise by the end of both dramas, which characters I might be referring to. If you drop either of the dramas too early, you won't find out :(