Propane Bottle selection
The question of aluminum, steel, or fiberglass bottles has been discussed in the past. To help you with your choice, note the following:
All metal cylinders must be inspected and re-certified after 12 years. The re-certification is good for an additional 5 years. This applies equally to aluminum and steel bottles. See the link below:
http://www.propane101.com/propanecylinders.htm#cylinderrecertification
The fiberglass bottles are initially certified for 5 years. Then they must be inspected and re-certified for each additional 5 years up to a maximum life of 15 years. See the link below:
http://litecylinder.com/faq/
Most propane refill stations are not licensed to inspect and re-certify. This service may be difficult and/or expensive. I have personally never had this done.
Given the cost of aluminum, steel, and fiberglass, the lowest cost per year is probably the steel cylinder. The fiberglass has the see-thru capability so you can see how much is remaining, so that is probably an advantage.
Your money, your choice. FWIW, I am about to replace my aluminum tank this year with a steel tank, and I sail in salt water.