We have a desktop computer, and need a 2nd unit.
whats the current trend and why?
There seems to be multiple choices in laptops, notebooks, Surface books, etc etc......
principal use would be a secondary unit for some browsing, paying bills online, and so forth.
What are the primary differences in laptops and tablets?
Do you want a keyboard? If so, laptop. If you hate laptop keyboards and mousepads like me, get a desktop or a dock for the laptop. You can use the laptop just like a desktop at home and/or work, plus the ease of taking it mobile when needed.
If you need something small to check the 'fire and email and general browsing, get the tablet.