I think you can upload larger GIF files using the “Add Images” button, which would upload and host the GIF on Imgur.
The reason there is a limit to uploads is to save bandwidth on the forums server. I’m not sure what the file upload limit is set to currently though, so it might need to be increased for larger files.
Uploading to YouTube as an unlisted video may be the easiest way to have longer content that can be easily embedded. YouTube also allows for he video to, optionally, have audio as well. I think Vimeo embedding also is supported.
On a whole though, as long as there isn’t tons of large files being uploaded all at once I think it’s fine to use whatever works best for you, whether it’s uploading or embedding :)
