I think taifa is more institutional and nchi is slightly on the emotional spectrum since it refers to land. 'I love my country' sounds more usual than 'I love my nation'. 'Nation' and 'country' are similar in English. But they overlap, and it would not be right to label 'country' as wrong. Both should be accepted. A citizen in Swahili is Mwananchi (and I have never heard Mwanataifa) but it is interesting that people who want to say 'indigenous citizen' - that is a native Kenyan as opposed to a naturalised Indian or European) there is the word Mwenyenchi (owner of the land). Not long after independence in Kenya this was an issue as Wazungu and Wahindi claimed passports and IDs, and black Africans were worried about their possible loss of ownership of the country.