Informative but entertaining video on high power DC transmission from Electroboom. To my recollection it’s generally always better transmission wise except the DC-AC and AC-DC converters are both expensive and physically large.
Both size and cost are dropping pretty quick with the development of better MOSFETs - the same ones that are soon to get very cheap because they're used in electric car motor inverters. I predict that in 100 years the majority of big power links will be DC (although we'll probably still have an AC grid too)