A very good question.
Some people will tell you that ProRes is a better codec, with a much higher bit rate, and thus converting your H.264-encoded MP4 to ProRes will improve its quality. It absolutely will not; it cannot add detail that was not included in the original MP4 file.
Some people will tell you that ProRes is an easier codec for editing software to handle, and insist that they must
transcode to ProRes before they can edit the file. These people all seem to be Mac users, and all seem to be using Final Cut. I have no experience with either, so I can't say for sure. All I know is that Adobe Premiere Pro was designed to handle the H.264 codec natively, and it works like a champ.
The only thing left: correcting D-Log footage by adding the missing contrast and saturation. This can be done pretty easily in Premiere Pro via the Lumetri color panel, so I don't see the point in the transcoding tool. I did an analysis of the original transcoding tool, designed for the X3 camera, here:
Again, this video is analyzing a different tool than you asked about. But I think the general idea is the same.