I would go with 2 lengths of 14m. If you do that, you'll have a total of 5 more meters of cord and still be able to use your carrier if you only need one piece. 14 m is like 42 ft right? I don't foresee you having to use much more than that at one time anyway and a double sheet bend would hold for just about whatever use you might have for joining the two pieces of line, short of rapelling.

so 2 pieces of 42 ft = 82 ft, verses 1 piece of 69 ft. Go with longer and learn some good knots.

--Matt