[Speedslug]

Your torch type and the size of the work you do are going to be the major factors here.

Yes natural gas does burn a little cooler than propane but unless you are working 3 inch marbles or working Boro into large pipes or other toys you may not ever notice the difference.

There are going to be zoning laws about propane tanks and getting them refilled.
Some communities just flat out wont allow them. They usually don't allow tanked oxygen either.

Your city building inspector will know.

Mainly your torch will make up your mind for you.

If you can go with natural gas I suggest it.

You can always change to propane later should you decide that you need the extra oomph.

Lots of people wind up with both.

Natural gas for the day to day stuff and propane for raging the torch and getting sun burned by the radiant heat.