They are both similar. One penetrates and the other regains health. They only differ in stability range and a little bit of impact and fire rates.
I have both but can't decide which to use more.
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Suros is ok at medium-close range but then you deal with shot guns cause the slow rate of fire. Hardlight is amazing at medium-close range. I hardly notice the health regen when I use Suros but I put up more kills with Hardlight tho.