You should only do the new route in NG+ since it is better to do the old route on any% because at 0:50 in the video below you will see a wall on the left and somewhere in that wall is a damage upgrade which makes fighting hive enemies a lot faster and easier.

(These two playthroughs of the game are tasses {Tool assisted speedruns} I played the game frame by frame and if I mess up ever I could rewind it. Neither of these tasses are perfect but they are good enough to show the new route is faster

Also tasses are not allowed to be submitted as rta runs but if your making a guide/forum post it's fine (you probably shouldn't claim your tas as an rta run in a guide/forum post though)