Banner tow to pay the bills if you must. But instruct! CFI/II/MEI time is looked on more favorably by an airline interviewer than pure banner tow time. You can get hired with just banner time (or pipeline patrol), but you will be behind the guy with equivalent time instructing, and overall you will probably need more of it. You will do better in training generally with quality instructor time than just banner towing. Having a CFI is always better for an airline interview than just the commercial alone.