straight edge, its very easy to wander either side of a chalkline/laser line, I tend to use a variation of all three, if its to bright to see the laser then i ping a line but always use a straight edge with both
If your sub floor can be screwed in to , i will suggest that you snap a line then spray the line with some clear varnish, then screw in to the floor a alluminum or wood straight edge, and start layng the tile against the straight edge keeping in the account the grout joint.