i think it depends on how picky you are about the consistency of your yogurt. for me, i'm picky. i want thick, creamy yogurt. so i heat mine, and i find that makes a big difference. i also do kefir and so for me it's just not worth making yogurt if it's going to be runny. but others prefer to preserve the integrity of the raw milk and aren't as concerned with consistency, and that's alright too. you can always strain it a bit to thicken it up.
another option: www.culturesforhealth.com
sells room temperature starters that work with raw milk. i tried one, but we don't climate control our house and the temperatures vary widely throughout the day and night, so it didn't work for me. but if you have central heating and cooling and keep your house a pretty consistent temperature, or at least have one area that you can keep consistent, i think that is a fantastic way to go - preserves the integrity of your milk, is less work, and creates a consistent result (and the starter can be used over and over if you follow the directions properly and keep a clean starter). so that might be your 'best of both worlds' bet.