United Technologies Corporation (NYSE: UTX) and Ingersoll-Rand (NYSE: IR) are key competitors in the heating, ventilation, and air-conditioning (HVAC) market, and combining their respective outlooks will tell you a lot about industry prospects in 2018. As such, let's look at which company's HVAC operations had a better fourth quarter in terms of results and outlook: United Technologies' Carrier or Ingersoll-Rand's Trane.Frankly, both stocks are attractive investments.