Property One for me.
You might be able to put a stairs to the loft in Property One if you started them in the cupboard in the bedroom. Or a spiral staircase. I don't know how much gear there might be in the attic associated with the solar panels but you might be in for a bit of electrical expense if you sere to convert the attic. Or maybe you could bump out over the existing kitchen extension or knock out the kitchen wall where the back door and utility area are and create a bigger kitchen with a room over it too. Maybe extend all the way to the party wall.
I prefer Property One. I sense a good deal of 'deferred maintenance' in Property Two (aka very expensive surprises as you remodel).
Love that long back garden in One too, and the fence looks nice and sturdy.
Property Two needs a comprehensive gut job.