As long as both the trades are made by mutual consent, and that the bananas are the rightful property of the person selling them, and the money you used to buy them with is rightfully yours, then both trades are equally ethical. The corollary is that there is nothing unethical in what two (or more) people agree to do that is mutually consensual, and which does not initiate force or violence against non-participants.

This is one of those situations where it is helpful to know the details. If you know the details, you can apply a logical analysis and decide what is more important to you. What are the benefits of fairtrade? The benefit is primarily to small farmers, who recieve some protection from competition by large plantations, as well as higher returns for their crops; and to laborers who are hired by large plantations, since Fairtrade standards dictate that plantation workers receive a certain minimum wage for their labor. The benefit is also to both workers and the environment in that chemical use is supposed to be limited, and the most dangerous pesticides not used at all. For more explanation of the Fairtrade standard, see http://www.wildoats.com/u/department74/. What are the benefits of organic? The benefit is primarily to small and medium farmers, in that large, high-production plantations are not interested in organic production; going organic assures small farmers of a niche market where they will not be competing against the plantations for sales. Also, the return for organic bananas is ~20% higher than for non-organic crop, which means that even if they sell less, they get more for it. The benefit to the environment lies in that organic standards mandate extremely limited or no use of chemicals at all, which has been shown to improve worker health as well as soil health. Limits to organic banana growing, however, lie in that some banana diseases (like Black Sigatoka and crown rot) have no organic treatment. Also, since plantations don't generally go organic, buying organic does not benefit plantation workers. So you can at least make a choice based on more information. Do you want to benefit small farmers, plantation workers, and the environment only moderately? Or small and medium farmers and the environment to a greater degree? For myself, I buy organic, because there is a further step which is important to me. I figure, the more demand there is for organic, the more small farmers might be interested in growing organic. The more interest there is in having organic-certified farms, the more push there will probably be to find non-chemical ways to tackle the plant diseases that target bananas. If we are lucky, it may lead to development of new domestic cultivars, increasing genetic diversity. At the moment, virtually all crop bananas in the world are clones of a single strain, and as such are incredibly vulnerable -- they all succumb to the same plant pathogens. I personally think that is a daft system, and opens up the crop to disaster in the long term. And because I like bananas, I want to see a more stable long-term future developed through the introduction of genetic diversity.