I've been using Spiro S42s with a Oliv G for almost three years so those are against what I'm going to compare the Perpetual set that's been on my bass for the last 10 days.
Tone: A very well balanced set with a G string that sounds like you're playing a bass from the get go.
Tension: They feel looser than Spiro S42s, closer to the Oliv G. They have a very nice bounce. Might like a midge more tension on the E but that's maybe because I'm still playing them as I play the Spiros.
Touch: They are very soft to the touch and easy on the fingers.
Arco: This is very subjective, but I find them to bow better than S42s. They start much easier and I can play with more dynamics (especially piano) with cleaner notes. I get much more scratchy noises with Spiros. Even better than how I remember Evahs.
Volume: I found them to be loud; even louder than my previous setup but it's not a fair comparison since the brightness of a new set can be deceiving when you compare it with older strings.
What would I like to be different on these? and this is personal preference: a thicker G string. Might be that I'm spoilt by the Oliv G, but I'm not a fan of thin G strings; I like to feel more meat under my fingers.
Last but not least, the yellow silks are a beautiful, subtle yellow.
I recorded some quick clips with my old Spiro/Oliv set, the Perpetuals/Oliv G and the full Perp set but I don't know how to post them. Suggestions?
Will these stay on my bass? Yes, at least for a while and then they might replace the Belcanto on my son's bass. He liked thema lot on my bass.