I remember ken raising an eyebrow to me saying I enjoyed spirocore reds for arco playing a while back haha. I've been using a set of belcantos per recommendation from ken (which I love) for the past six months. I think kens description of the spiros being edgier & belcantos being smoother is spot on. Sometimes I feel like these 2 sets would be suited for different composers work rather than a jack of all trades set. I miss my spiros sometimes (which I put on a Romanian flatback I rebuilt & sold to a jazz player) for getting a nice beefy forte on Beethoven pieces. I use black hair & med oak rosin always on both sets by the way.