First, it is worth pointing out, that to create a multi-site implementation in Sitecore, you don't need any of the modules you mention. Sitecore supports multi-site out of the box - you just need to set the configuration in the
<sites> node to point domains at the right part of the content tree.
Having said that, here is overview of the 3 options:
- Sitecore Foundry - AFAIK, Foundry is not supported on the latest versions of Sitecore. The module hasn't been updated since 4-17-2015, so I would not consider it an option.
- Multiple Sites Manager - does look like a good option. It has a good team behind it. This would be a good fall back if you don't have SXA
- SXA - This would be my choice... if you have the license for it. Remember that SXA is an extra license for Sitecore 8.2. Also, this is a good option IF you plan to build your site using SXA. If you are only looking for multi-site options and you want to custom build your site, then this would be overkill. Just roll your own out. BUT if you take advantage of all that SXA has to offer, it is the best option here because of all the extra enhancements that you get with SXA.
Ultimately, the best option comes down to your implementation. If you plan to build the site with SXA, it is a great option. If you don't have the license, or just want to build everything custom, Multiple Sites Manager also looks good. And remember, you can always roll your own solution out.