Size
The Broholmer is larger on average: about 55 kg (121 lb) as an adult, against 35 kg (77 lb) for the Rhodesian Ridgeback.
Shedding
Their coats shed differently: the Broholmer moults most as the seasons change, the Rhodesian Ridgeback sheds through the year.
Exercise
Plan for plenty of exercise with the Rhodesian Ridgeback, and a moderate amount with the Broholmer.
Temperament
They differ most on independence (Broholmer: cooperative, with its own ideas; Rhodesian Ridgeback: decides for itself) and on handler demand (Broholmer: needs steady training; Rhodesian Ridgeback: needs an experienced owner).
Alike
Both are rated the same on loyalty: sticks close to its people.