First question: Can BLACK SABBATH be compared with BLACK SABBATH? I don't think so, the eras are too different, but in music and vocals, even though it always has been BLACK SABBATH.
"Headless Cross" can barely be compared to the beginnings with Ozzy Osbourne, because firstly the music here is quite epic, but still powerful Doom and secondly Tony Martin's voice alone is so very different...
But anyway, "Headless Cross" stands in one line with the long series of classics and after a short keyboard-intro the title-track impressively shows what is BLACK SABBATH: Majestic riffs, a very good flow of the song and, of course, Martin's brilliant vocals. That there is a bigger emphasis on the melodies (also or maybe just because of the keyboards) than before doesn't place any flaw on it.
The two following "Devil & Daughter" and "When Death Calls" keep the extremely high level and also offer epic Power Doom of the top-class. After that it turns a little more shallow, because the compositions turn a little catchier, unfortunately not keeping the same emotional/atmospheric depth than the first half.
Still "Headless Cross" is essential to everybody, who feels even just roughly appealed by the above-mentioned sounds!