Considering the cost of labor and other operational expenses as well as the exchange rate between currencies should help you draw a more accurate conclusion in terms of business expenditure.
A developed IT infrastructure and high availibility of talent as well as cultural compatibility would ensure your demands are understood and met with precission.
The proximity of the nearshore location and language proficiency makes comunication easier and increase productivity.
Lastly, the nearshore location should have a favourable legal framework in place for IT outsourcing and data protection.