I have never used map gas and have only used propane. I didn't know if it is a bad choice. Years ago I was trying to soldier a 1" line to repair a leak in the yard and propane wasn't doing the job. I had to get an AC buddy to bring over his acetylene torch and it did the trick. Another reason is I could use map gas to help with sturborn bolts too. I agree, prep is important, but sometimes having some extra heat coild help.