good question.
if the amount of data transfer huge? are you processing multiple data files and need transactions (both at file system level and database level)? are you dealing with multiple data sources at different locations (for eg ftp, local file system, database)?
if answers to above are yes then go ahead with ssis. basically .net is cool with small data import / export jobs, but when you have anything more complex, ssis is a definite winner
the other thing which i look at is – is it worth writing .net code when everything is available inside ssis. (dont mistake me – i love coding) however, anything you code, you need to maintain 🙂