Clearly each Spanish speaking country would proudly argue the point that the Spanish spoken in their homeland is the best! And who would expect otherwise? Culture and language are intricately linked and each country has much to offer visitors from a culinary, historic, artistic and linguistic perspective.
With that stated, a strong case when choosing a country for an experience beyond a sightseeing visit, but rather to learn Spanish and delve into cultural subtleties, is to investigate which country is best for your linguistic acquisition. Spanish can be classified into countries with clear diction and a certain level of linguistic standardization.