I've not read either of these books, although I know Rosemary Sutcliffe via "Eagle of the Ninth" and other books.
Novels related to Arthur that I have enjoyed ( historical or not ) have been the Bernard Cornwell series [ yes, Agraes, I know, but this is a novel) ] plus the Jack Whyte novels [ Sky stone, Singing Sword, Eagle's Brood, Saxon Shore etc ] which attempt, quite well, to provide a decent and believable historical background to the Arthur myth. Personally, they do become tiresome after a while, but maybe I read too many of them together. {PS. Avoid his Templar novel series "Knight of the Black & White", etc . Total and utter bullsh1t in 600+ pages...waste of time and money, sadly some of it mine( 9.99 Euros ! anyway ) }
"Conscience of the King" by Alfred Duggan, recently re-published, is an undeniably realistic, pragmatic and blunt re-telling of the fall of the Romanised Britons, and creation of the Saxon petty Kingdoms in the late 400's.
Devoid of political correctness ( written, I think in the 1940's or 1950's ) this is a novel of the Saxon invasion with, in my opinion, an RTW view of the reality of life and battle in the 480's plus. Establishing the kingdom of the West Saxons ( via Aelle & the South Saxons ) it is simply written, but nonetheless very engaging. No cinematic battles, but in true RTW style the significant ones involve only a couple of thousand men at most and decide the fate of tribes/kingdoms, if not ultimately nations.
For a more "romantic" ( and I mean the higher value, not man/woman ) , but very well-written and enjoyable Arthur novel, try TH White's "The Once and Future King" ( this became Disney's "Sword in the Stone" but please, read the book, it is real literature ! ). A boy becomes a man and experiences life including the final battle with "Mordred"...a true experience.
Other novels set in similar times include George Shipway's "Imperial Governor", for example.
Lovers of historical novels should really check out Alfred Duggan,
His "Winter Quarters",covers Roman Britain and Gaul.
'Three's Company" is the triumvirate of Lepidus, etc I remember one about Elagabalus, a very youthful Emporer as Rome fell apart. Another was "Lady for Ransom" set in 10/11th Century Constantinople and based on a true ranson attempt from thos edays.
I read them years ago when my dad had a few of them and I bought some more to read. "Count Bohemond" is an un-matched, non-politically-correct novel of the Crusades...wonderful in its realistic view of the 11th century from a, possibly skewed, 1950's Britain, but none-the-less accurate and absorbing.
Maybe a digression, but if you enjopy reading historical novels with a realistic view do try Alfred Duggan - much under-rated !
You guessed, with books, I can go on all night..