I have experience of both, my MiL lives in council provided sheltered housing and it was rented funded 100% by means tested housing benefit. She lived in three in total, 1 in Stockwell, London, where the community mental health nurses were brilliants and the accommodation ok but very secure, 1 in Epping, which was truly awful with zero community nurses, very old, damp and not secure, and the final one much closer to us in Essex, which actually was ok, only a studio flat, but very secure, nice new kitchen and wet room and shared communal areas were cleaned and maintained. Laundry onsite and a hair dresser and chiropodist visited weekly. Biggest issue was AFTER we moved her in the live in Wardens were cut, due to cuts in Council Services/Budgets instead of having one warden per premises they cut the numbers and had 1 per three premises.
My close friends grandmother purchased privately a very nice large one bedroomed ground floor flat, with French doors opening onto the lovely communal gardens. Lots of lovely communal space and lots of activities.
My only comment is that all of them, rented, council or purchased appear to vary enormously. About 5 miles from us permission has been granted for a retirement village, on paper it looks and sounds fab. Good luck in your search and really really think hard before you make a decision.