KitPvP has a diverse variety of kits, and there's many options to choose from that all vary in play style. However, some kits are more commonly used than others, which I will cover in this analysis.

What are the most used kits?

This is based on the KitPvP playerbase that actually plays the game and has a solid main kit, not the visitors that all have default 1

Viper (15%). Viper has the strong ability to give your enemy poison on hit, which is why it appeals to many. Also, the armor gets really good at high levels.

Zombie (15%). Zombie has really powerful gapples, and armor that gets really good at high levels, like viper.

Enderman (12%). Enderman gives infinite speed 2, reliable gear, and a great ability.

Kangaroo (12%). Kangaroo has decent gear, feather falling, and a cool ability which allows you to escape fights.

Archer (10%). Archer has infinite speed 1 and a powerful bow.

Fisherman (8%). Fisherman has strong gear and a rod that can reel players in.

Default (8%). Despite being the default kit, some people stick to this kit because of the solid melee gear.

Dragon (5%). Dragon gives reliable gear and a strong fire ability.

Boxer (3%). Like default, boxer also gives reliable melee gear, however it's a bit more expensive, but gives a good ability.

Dracula (3%). Dracula gives a lifesteal effect, effect stealing, and solid gear, but it's pretty expensive.

Stormcaller (3%). Stormcaller gives an ability to summon lightning to enemies around you, and some good armor. However, the weapon is pretty bad and it's somewhat expensive.

Other kits (5%)

Takeaways from this

1. People like to have reliable gear and abilities. Take zombie and viper, for instance. They both get good armor, and zombie gets strong gapples while viper can give poison on hit and gets slow pots. Dragon also gets strong gear and a fire ability. Meanwhile, enderman gets reliable gear paired with infinite speed 2 and a strong ability.
2. People like cheap kits. Legendary kits are rarely seen, because they take so much money to buy and upgrade. This is why viper and zombie are so popular, as they are so cheap. However, price isn't the main factor. Enderman is much more popular than sonic because although sonic is cheaper, enderman has much stronger ability and armor.
3. People like easy to use abilities. Fisherman isn't as popular as viper and zombie because although it has much more reliable gear and the same price, the fishing rod ability is pretty hard to master, while zombie only requires eating gapples and viper's ability applies automatically on hit and slowness pots which are self-explanatory.