Storing images inside the file with balloon your file size at a huge rate.
I use 'by reference' all the time, and have never noted it to be slow. It is pulling the image in across your network (or from your HD) so the connection speed is a factor. As I say, referenced to a local file or a LAN server has never caused me any problem.
You must plan that all users of the file have the same reference path to the images - so they must all map the images' folder in the same way. That may give you a issue with making sure the iPad can also see the same image path.