As a result, the only differences are those that emerge from how the text is generated – in a focus group the researcher generates the text under specific circumstances, whereas usually in textual analysis the texts already exist and are chosen by the researcher. So what concerns emerge? Lunt and Livingstone talk at length about communication – the interactions between people in the group. The group dynamics of a focus group are certainly one of its unique benefits and not something that can be replicated in textual analysis. I do think it makes sense to talk about communication in terms of texts, though. Different texts can be seen as part of the same broader discussion or discourse. They may not speak directly to each other (although sometimes they do), but they're still involved in communication. In studying texts, we do miss out on the specific interactions and direct responses of a focus group, but we can gain a broader sense of how topics are discussed.
Lunt, P. and Livingstone, S. (1996). Rethinking the focus group in media and communications research. Journal of Communication, 46(2), 79-98.