Decrease FPS of too-high FPS video or increase FPS of too-low FPS video? I created two videos of the same scene with two different cameras. The issue however is that camera 1 captured everything in 23.85 fps and camera 2 everything in 24 fps.

Since I need to synchronise both videos exactly, it's quite essential that the frame rates are the same. I'm however not sure whether to decrease the 24 fps video to 23.85 fps or increase the 23.85 fps video to 24 fps. Thanks in advance for your advice!
I think the answer depends upon what frame rate you want to deliver your video at. 

In general it is better to shoot at the delivery frame rate. 

I agree they probably won't go far out of sync if the clips are only short (a minute or so). 

If you do need to adjust them, I would frame rate adjust whichever clip is going to be on screen for less time in the edit (or is less important to you).