You'll be hard pressed to by a netbook now.
Netbooks underspecced for everyday use, but do have the advantage of size and glovebox friendly. Low screen resolutions tends to cause trouble with manage laptop based diagnostics kit. They definitely have a place in life, but I'm a bit wary of recommending them due to their downsides, any potential buyer needs to know their requirements before committing 
I wasn't recommending anything. But a netbook is ok for diags with a stick of ram. Therefor, anything will do for diags. That was all.
The point being, just buying a decent lap top is the priority. As diags will just work.
Did I mention not to worry about diags? ....and just look for a decent machine.
Jeez.

Aye, no diags software should tax a modernish lappy

Beware, if your diags hardware relies on bit bashing a serial port, go for a laptop with a proper, genuine COM1 port, as most will struggle through an adapter, even modern, fast laptops. This tends to be older diags hardware like cheapo tech2. Proper serial ports do not exist on modern laptops.
Size wise, that's preference. I like the smaller size of the type mrs gixer has. Perfect compromise of portability and function IMHO. Some prefer the extra size of those with the wider screen, and don't mind the reduction in portability. Netbook is what gets thrown in suitcase for holidays etc.
Obviously I'm lucky enough to have a couple of dedicated laptops for diags (both older, both with real serial ports).