There are two kinds of trackers, content-wise: specialized and general. General trackers will often serve the majority of your needs, while bigger general trackers will usually have plenty of niche content.

Popular public trackers are general trackers: RARBG, RuTracker, ThePirateBay, etc. Due to their broad scope, they will still never match the niche trackers in their particular area of specialty.

The following is a global consensus on what is considered the best tracker in their fields, namely: Music, Movies (both mainstream and obscure), TV, HD (yes, this gets a separate category), Games, Books, E-learning, Porn, Anime, Scene and General.

Green trackers are the cabal — the holy trinity of PTP, BTN and HDB + RED (This is known as the /ptg/ diamond). These are the best, most reputed trackers in the torrent community.

They are objectively the best in their respective categories and rule the torrent world. Do not fuck with cabal staff as they will gang up on you and have you permabanned from all cabal trackers along with any other trackers willing to cooperate with them (and many often do).

Yellow trackers are subject to the cabal — if you're banned from the cabal, you will get banned from these as well. On the other hand, a good ratio proof on one of these will be well-considered if you apply to another cabal-subjected tracker. However, because of their niche or subpar content, they don't get as much exposure as the cabal.

Red trackers are primarily shady — they are either the IPT mafia empire or are run by staff known for shitty practices such as trading accounts, DDoSing other sites, encouraging pay2leech and storing passwords in plaintext. They are the cabal's worst enemies, so don't expect ratio proof on one of these trackers to be taken into consideration on cabal sites. They may still have good content and be worth joining, just don't give them any money for any reason whatsoever.
Being in the cabal means you can afford to give little to no fucks about your account on one of these. For instance, if your IPT account gets purged, you can just get another one.

White trackers are either open or not known to cooperate much with the cabal, but they aren't known for shitty practices either.
Light blue are semi-private and public trackers.