There are other factors such as time, pain, possible failure with equipment. The PPH in the wiki under sources there is a link. Most rate Nembutal (A Barbiturate - Essentially what was used before Benzos , but a lower safety profile. It's very peaceful and is as effective as they come. However it's very expensive and hard to get, you'll see posts about N from person #1. It's going to run you possibly $1,000 only available from south Americans vets, and a few other countries in the region where people will go to these regions to buy it there due to the lower cost and scams, but can still be tough to buy (it's used therefor putting sick animals down.) It's generally very peaceful and you go to sleep. Don't try this with Benzos (Xanax, Ativan, Klonopin) as you would have to take a thousand pills with higher safety profiles.
Easier and quick but more mentally tought is a 12 gauge shotgun with a slug in your mouth.It'ts easier to get and works 99% of the time but is not a pretty after scene and some have a fear kick in putting a gun in your mouth or a family member seeing the result.
The newest method is an inorganic salt called SN. There are many threads about it, is cheap and is the choice of many now. There are other methods but these are the top 3 talked about. Read the wiki on SN to get a better idea. It's a choice, some will suggest helium, hanging or large doses of opiates. You should read pros/cons and your situation with your financial resources, living with others, and your comfort.