I think you’re right – using Ai files would be my usual choice. The artist normally uses Photoshop and he’s not so familiar with Illustrator, so wanted to weigh up the pro’s and cons in using both types of files. I think he’s willing to give Illustrator a go though.
As the animation is going to be quite complex, the file sizes are definitely going to have an affect so thanks for the advice on that. I want to try and avoid long render times and large file sizes if possible!