Well then, let me lay out the ups and downs of each class.
Musketeer. Medium/High health, made for amateur/veteran players. Uses traps, bombs, barricades, and long range moves to kill enemies while they are still far away. Musketeers get good companions, like the much sought after Ridolfo Capoferro, a Unicorn companion from Valencia, which is unique to the Musketeer class. Musketeers get Chantal Livingstone, a deadly Flamingo Marksbird with insane amounts of power and deadly moves.
Witchdoctor: Low/Medium health, made for master gamers. Witchdoctors get FEW class unique companions, most of which are animals and creatures. However, their ability to attack up to NINE targets at once is significant. Also, they can cast curses and other moves that have infinite range, unlike musketeers. Witchdoctors get the powerful Carcarius Grimtooth, a deadly witchdoctor that can deal out tons of damage and has a high critical hit ratio.
Both classes are good, but ultimately, it's up to you! Have fun in the skyways!
I agree a lot with warrior creed, there is not a lot more I can add, I have made a max musketeer and witchdoctor before and I must stay they both were very new experiences for me, I lot different than my first 2 pirates buccaneer and swashbuckler. Witchdoctors and musketeers can attack enemies while staying in the same place during the full fight. Even though musketeers have better companions I prefer witchdoctors. They have spells that can attack a lot of enemies, but so does musketeers. Musketeers also get good talents like quick draw, double attack, etc, all witchdoctors get is mojo echo, it is useful but if you are a witchdoctor you wont need to use regular attacks very often. Witchdoctors I think get the most powers out of all the schools, no matter how long the battle is at a certain point it is almost impossible to run out of powers. Their powers include mojo bursts which can attack as many as 9 people as once, summon undead to fight for you, jobu spells which drain bad guys and replenish your health, mojo blade which do A TON of damage but you have to be right next to your attacker, spells that go in a straight line and do a lot of damage, etc etc. Witchdoctors have the least amount of companions but the most powers. Even though witchdoctors get good school companions like mormo, grimtooth and kan po I think musketeers have better ones overall. They get a lot more and most of them are good. Musketeers also have a large amount of powers as well as more health. They have lots of traps, and other good long range attacks. Both schools are really good, it just depends on what you want, do you want a better selection of companions for questing or you want a ton of strong powers, big attack companions with very low health.