Re: Using LR5, would making development adjustments on the RAW file, with conversion to DNG in export, give a better result image, than converting to DNG on import and then doing development adjustments on the DNG file?

Proprietary raw files CR2 NEF, etc, and DNG, are ALL 'raw' files.

There is no difference editing either in Lightroom.

Converting all files to DNG has some advantages- but that is the big debate for photographers!

Edit adjustments are all contained in the Lightroom Catalog. (Be sure to have Catalog backups!)

There is no reason to Export as DNG unless you want other people to view your DNG in an Adobe program.

If you Export, then it is more likely you will export a 'pixel' file type-  TIFF, JPG, (Photoshop PSD ) etc.