What is the ideal format to work with my designs, AI or PS?

I create all graphics and illustrations in Illustrator, put every element that needs to be animated on a separate layer, and only convert Vector Layers to Shape Layers in After Effects if I have to use shape layer animators, edit the actual vector path, use a vector path as a motion path, or extrude a layer. Converting AI layers to Shape Layers always increases render time. Most of the time, my elements (layers) are in their 'hero' position, so I can easily animate backward to create the transitions.

If an illustration has a photographic component, I use Photoshop. Again, animated elements will always be on a separate layer, and I tend to use a lot of layer groups.

The best workflow suggestion I can give you is to create comps that are only one shot, then edit in Premiere Pro. My motion graphics comps are seldom longer than one sentence of narration, never longer than one idea. If I need a smooth transition between shots or sequences, starting the next comp where the last one ended is easy. All you have to do is copy and paste some layers and adjust the in-point.

If you open Media Encoder, then pick a good visually lossless Production Format, you can keep working on the next comp while the first one is rendering. This is a tremendous time saver. When the client what's a change in a shot, you don't have to re-render the entire video from scratch. It sounds like more work to create 40 comps for a 10-minute video, but it is a lot more efficient, and you'll get a better product in the end because you can fine-tune the final movie a lot easier and faster in an NLE than you can in AE.

Workflow is always more important than the file format of the source files. 

I hope this helps.

Sorry, but that's a pretty pointless question if you don't show us anything and do not provide any info about your computer, how the assets are used and so on. That being said, based on your description it is unlikely that the format of the assets even matters. Unless your animations are super complex, chances are that there would be zero difference. Whatever performance issues you have will require other solutions.

Mylenium