I would pick the NH hotel. I'm not sure what brand the Accorhotel is but unless it's a Sofitel or Grand Mercure the NH hotel is probably the better hotel in terms of quality and service.

Neither hotel chain has a great loyalty program. Accor has many hotels in Europe but most of them are not really inspiring. Gone are the days that I would fancy a stay in an Ibis or similar hotel. If you compare those brands to the budget chains of Marriott..... well, there's really no comparison.

NH has good hotels, many of which are also in good locations, but unfortunately, the brand is only present in a small part of Europe. (with a few outliers in S-America if I'm not mistaken)