Are Tier 1 panels better than Tier 2 or 3 panels?

Not necessarily. For example, you need to be a very large company to become Tier 1. Lots of little 'boutique' manufacturers make excellent solar panels but will never be classed as Tier 1 as they don't ship enough volume.

Eh? So why do you recommend only getting Tier 1 panels?

Because unless you have deep knowledge of the industry, you won't be able to judge if the small panel manufacturer is a top quality boutique manufacturer or absolute junk being shipped to Australia because no one else will touch it.

If you insist on Tier 1 panels, you know you are getting a well regarded brand with good support, good quality control and warranties. If you don't insist on Tier 1 you are alone in the dark!