As far as I understand, the difference between a normal laptop and a tablet would be your screen and input. A normal laptop, like a desktop has a keyboard and a screen. A tablet laptop would be mostly screen and use a stylus to input (though they may also have keyboard inputs). Not sure what kind of linux support is out there for tablets (not my cup of tea as far as laptops go).
As to what kind of laptop to get, you have to start with how you expect to use it. I use my laptop for taking notes during meetings, sending email from off site and administering systems from off site. Both the email and administering happens when I'm away and it is some sort of emergency. For my use, the most important thing is small and light so that I will take it with me. If the keyboard is a little cramped, that is a small price to pay.
I use a sharp mm20. 100% linux compatible and never booted into Windows.
Other people expect laptops to be mobile desktops as such the weight is not as important. I have had pretty good luck with Toshiba laptops for such uses. The best thing to do is find a laptop that will do what you want and then search for linux compatibility.
For me the big deal breaker the limited increase in usability compared to the sizable cost increase for a tablet. Expect to pay more for a tablet with the same processor, memory, disk space, etc. as its ordinary laptop cousin.
As with the last poster I don't know what kinds of drivers are available to get a tablet's touchscreen to work in Linux. Some of the 'cool' things that you can do with a stylus are software dependent; hence the special version of Windows for tablets.