Am I right to assume you can enlarge .ai files without reducing the image quality? Are these vector files?
Also, can you click & drag the object to make it bigger or do you have to use the resize tool where you put in dimensions?
You can import .ai files as Smart Objects that can be resized without any loss in quality by going to:
FILE (top menu) > PLACE
or on a Mac:
Photoshop (top menu) > PLACE
Yes, you can click and drag the object to make it bigger.