Why is focusing on the breath more difficult than focusing on Mantras, and how important is it before vipassana? I have been doing mantra meditation for years and saying "Aum" for a few minutes makes me go deeper in meditation within like 10 minutes.

But focus on the breath is difficult compared to the mantras.

What is the difference between the results of breath vs vipassana?

I can hardly do 10 conscious breaths (feeling peace). Any suggestions for betterment?

On the other hand doing vipassana makes me feel very strange (like perceiving vibrations) in my entire body.

In mantra meditation, it feels like something (kind of waves) is coming out of my body.

Am I on the right path or is it hallucination?
When reciting a mantra you have vitakka and vicāra which helps you get close to the 1st Jhana. But this is also accumulation of Fabrications (more particularly Verbal Fabrications) which should be avoided.

Vitakka and vicāra without the constant awareness of arising and passing inhibits the ability to see impermanence. That is why when you are doing Vipassana you become aware of vibration but not when doing mantra meditation.

To aid you breath meditation you can use vitakka and vicāra to your advantage. Be aware that your are aware of breathing then periodically assess whether you are actually with the breath, but at the reducing frequency. Start with even in breath and out breath and when you notice you can stay a while then do it after each breath and then after few breaths and you your mind just sticks to the task then drop it altogether.

Vitakka and vicara in initial application and sustained application. 1st your bring your mind to the breath then this is the initial application followed by trying to keep the breath in mind.