I use both landline and multiple (pay as you go) mobiles. I find it's useful, that way, to separate different types of calls.
My parents and siblings call on one mobile and occasionally the landline.
My doctors/the NHS will use another mobile for texts.
When entering competitions, I give the ones that need a phone number a 3rd mobile number.
Some companies (Oakhouse Foods, Wiltshire Farm Foods and Virgin mainly) use the landline, as I don't want to miss them.
I also use the landline to order my medication, though not for much else, unless I'm out of credit on all my mobiles.
So, for me, it's best to have both types of phone.