I have both. Camelback for MTB or a long road ride with few places to get water. Bottles on the road or a quick easy MTB ride.
I prefer the bottles, it's more comfortable, but the camelback is not bad and it gives you space to stash all kinds of things. I have lost bottles due to ejection on the MTB, and I have drank mud on the MTB too.
Drinking from bottles while riding just takes practice.