Bioconda is a package manager that makes the installation of your tool easier. Most likely, this will be used by bioinformaticians that do their own analyses and installations (of command line tools). That means, the person installing and using the tool will most likely be the same.
Galaxy is a web-based portal, that is typically set up and maintained by an expert (e.g., a bioinformatician or a sys admin) who probably provides access to that server to other people, e.g. biologists in the same lab/institute that will use the tool via Galaxy's graphical UI. Therefore, the person installing your tool will most likely not be the only user of it.
Which route will increase your tool's visibility is hard to predict since bioconda and Galaxy have slightly different target audiences (with some overlap for sure, though).