[Joe Johnson]

This is not a simple question to answer.

Yes, in general, 14.5 degree PA teeth are weaker than 20 deg PA teeth, but unless the number of teeth are small (under 14 if you are looking for a rule of thumb) the difference is not huge.

Higher pressure angles are a generally good thing but not always. In the area of sound some folks claim they can get better sounding gears with lower pressure angles.

The major benefit of using higher pressure angles is that it reduces undercut for small gears.

To first order, you can get a good estimate of the strength of the tooth by approximating the tooth as beam and estimating what force the bending stress at the thinnest section of the tooth would exceed your material stress.

There are other places on these fora where these calculations are discussed. I don't have time right now to search for them, but I hope someone will and link to them.

Joe J.