How does Origins Comfort 1000 compare to softest Vispring?

Thank you for your very informatative site. I am 9 stone and 5'7", and have a single slatted bed.
From reading your site I think I need your softest mattress, the Origins Comfort 1000.
Before I found your site I was considering Vispring. How soft is the Origins Comfort 1000 compared to the softest Vispring mattress?