Best Meditation for Stress

I've been meditating using different types of meditation for years now. I've been feeling a lot of stress lately, and I want to calm down in the ideal way. I've been reading neuroscience studies claiming that breath meditation is the most effective to calm down the amygdala, a key brain region in stress. However, when I meditate on the breath, I feel somewhat tense. When I meditate openly (without object), I get shivers on my body as if I were getting calmer. During focused breath meditation, this doesn't happen. I'm having a lot of trouble figuring out whether, on the long term, breath meditation is really more calming than an objectless meditation or even of loving-kindness. **How can one know what type of meditation is most calming and de-stressing long-term?**