It depends on what you are trying to do. Smartphones and tablets have traditionally been good for consuming content--i.e. reading online news, watching videos, and listening to music.
To some degree, they have production value, such as providing brief responses to emails, posting photos on your social network, capturing videos, and tweeting.
If you want to do some heavy duty production, it is easier to do it on desktops or laptops, as they provide the option to view production content on significantly larger screens. They also provide more horse power for processing and doing more complex operation. In addition, the storage capacities on laptops and desktops far exceeds those of a smartphone or tablet.
So the answer really is it depends. If you only consume content, a smartphone or tablet is better; otherwise, go with a laptop or desktop.