Either 70-300 is going to be a non consistent aperture lens which isn't very good for video as it will make the exposure darker if you zoom in and will make a ticking noise that can be heard on the video. It's a cheap lens and for canon vs sigma it comes down to do you want macro or stabilization. Stabilization is probably the way to go with a minimum aperture of f/4 and that's only at 70mm. Don't expect either to be sharp lenses.
If you're serious about photography or think you will be in due time, don't waste your money on el cheapo gear and get the good stuff (70-200).