16/9. Is it a clever way of working.
Vectors may scale smoothly, but any raster/bitmap imports will compress/pixelate awful. Instead of giving a ratio, you should work to output. Is it for NTSC (american?) or is it PAL (uk), this will have an impact on your frame rate as well- 29.97 for NTSC and 25 for PAL. Is it for Widescreen television, standard television? Is it HD? 480p? 720p? 1080p?
My suggestion would be to work in a HD format. If its for a client, 1080p (1920px x 1080px) if its for yourself then 720p (1280 x 720) is efficient enough. Working at 480p is very much daft, as you means well go to a higher resolution such as Standard UK widescreen 1024x576.
So it depends on what TV, and where.