I like IS for images. Have been keeping a careful eye on average price per subscription but even with some really low commissions, my average is over 28 cents (which used to be the average). Many people will tell you to run from IS and for video, that very well may be true. IS is a pain for uploading.
We have the opposite numbers as you >3000 images and ~500 videos. We like 123 because it is easy for uploading (not categories, no keyword matching nightmares!) but our video sales are very slow there. With your bigger port, you might have better luck (and your port is likely better than our simple video clips).
All this to say, I'd go 123 with all of your files and maybe consider IS for your photos only.