For muscle relaxation? Diazepam. Easily imo.
Diazepam's specialty is muscle relaxation. The 2nd best clonazepam.
I have a rx for clonazepam and also have tried the other 3 most popular Benzos including Diazepam, Alprazolam, and Lorazepam.
Diazepam was the very best for muscle relaxation. It seems like the long lasting Benzos are better for muscle relaxation. The shorter acting ones including Alprazolam and Lorazepam
Are better for panic attacks as they do kick in much faster.
But yeah to answer the op Diazepam is best for muscle relaxation.