I don't think it's so much a matter of what one can do that the other can't it's more a matter of which is better suited to do the things you wish to do.
For instance, if you want a device to take notes for school, the Chromebook would be better suited to that since it includes a keyboard whereas the tablet doesn't. If your main use is to watch videos or play games, then a tablet may be best for you.
A Chromebook is a better choice for those that want to create content whereas a tablet is best for those that simply wish to consume content.