Any accent is suitable, IMO, although I personally dislike the carioca accent intensely. The paulista (from São Paulo state) accent seems to be less popular among learners, but overall I think you need to go with whatever resources you have available. Word pronunciation doesn't vary that much from one accent to the other, it's more an issue with intonation and a few sounds that are different in each variant. The 's' in the carioca accent sounds more like the 'x' in Chinese (like in xie xie) or the 'ch' in German (like in ich) while the 'r' is always gutural at the end of words, actually it's more aspirated than gutural, like in the German word 'doch'. In the paulista accent the 's' is mostly like in English. The 'r' sound is a different matter, since there are different pronunciations for the capital city variant and the countryside variant. Having said that, I should mention that paulista is the person born within the state of São Paulo, while paulistano is the person born in the capital city of São Paulo. The former pronounce final 'r's like the Americans while the latter always roll their 'r's. Other than that, it's mostly a matter of, like I said, intonation and vocabulary. Cariocas call a curb 'meio-fio' whereas paulistas say 'guia' and so on and so forth.
If you watch the news on Brazilian tv, you'll see that the broadcasters speak neither the carioca nor the paulista variant. It sounds more neutral, and I suppose that's a good standard to learn because it doesn't sounds heavily carioca nor paulista.