LRC IMPORT :DNG or Copy?

Agree with what was already said. There is no best choice. The debate mentioned (and this is one of those pineapple on pizza is it OK or not debates)

Use Copy: fastest import but uses a bit more diskspace in the end. Imported raw files can still be opened in camera maker's software such as Canon DPP or Nikon Capture

Use Copy as DNG: slower import. Uses less disk space (dng compression is more efficient). Imported raw files can no longer be opened in camera maker's software.

I use Copy as I don't care much about the disk space (hard drives are cheap) and rather have fast import but I sometimes exchange files by exporting from Classic in dng format so people get a nice little package with all the settings embedded. Those settings can only be read by Adobe software. It's also great for archival as Ian notes as dng is an open and documented format contrary to the raw files from most cameras.

While DNG is the file format that I prefer to work in when using Lightroom Classic it's not necessarily to best for everyone.  First, it takes longer to import the images as they need to be converted to DNG rather than just imported. You'll also need to decide whether to keep the originals as backups or duplicate the DNG as your backup. Personally, I do both but others customers are happy with one or other format as their backup. It's also worth noting that Adobe consider DNG to be best suited as an archival file format (not to be confused with legacy). It's more compact than proprietary raw files and develop settings, metadata can be embedded within the DNG file rather than stored in an XMP sidecar.

DNG is also ideal for cutomers who wish to continue using an older version of Lightroom with the latest and greatest cameras. However, this would require theat they first convert the images using the standalon DNG Converter.

"Best" is a word that has no definitive definition in this case, and can generate a great deal of argument.

There are pros and cons. An internet search will turn up huge amounts of discussion, debate and argument on this issue.

I use COPY. Works for me.