I stayed at the Crismar for one month (got a job in Arequipa for the summer), so I think I know what I am talking about. The Crismar is a basic, nice hotel. Location is great (walking distance to most of the Arequipa highlights: Plaza de Armas, Catedral, Iglesia de los Jesuitas, Convento de Santa Catalina, calle San Francisco, etc.); Price is great (around $40 USD for a renovated room: nice, clean, big, comfortable beds, cable TV, free Internet, modern bathrooms, tons of hot water); Staff is great (really nice and helpful).
El Libertador is a better hotel by far, BUT if you want to stay in a nice centrally located hotel (for one-third of the price), I would recommend the Crismar. As I said, it is nothing more than a 3 or 2.5 star hotel, but it is a really decent place to stay.
This review is the subjective opinion of a TripAdvisor member and not of TripAdvisor LLC