What is better 16613 ?
Depends what movement your looking for to use 3135 is the movement Rolex actually uses on their subs. If you want to use Rolex movement replica you can use a JF sub 16610 with 3135 movement as your base case and movement model and just add genuine parts like dial/ crown hands etc....
Now if you want a cheaper movement and easier to repair and maintain you can go with bp 16613 but I’m not 100% it is gen spec meaning there might be modding needed to place gen parts on the watch head as the dimensions are not the same as gen. But again I’m not too sure if BP has gen spec
Maybe another member can chime in about bp