Quality is OK although for £25 I don't expect top quality. It is purple so dark anyway and isn't see through unless you hold it up to the light but then most things are, if you hold them up. I don't expect it to go baggy or anything like that.
It is soft but not as soft as cashmere.
£59 is fairly cheap for cashmere so I would guess that in terms of quality, the two jumpers you linked to are on a par unless the JL one is a bargain. You need to find somebody who has tried that one too really.
I have meriono and cashmere items in my wardrobe. Personally I prefer merino because it is easier to care for, wears better and is still warm. I have pieces that are a couple of years old and still no bobbling.
I hate bobbling and I am afraid that this seems inevitable with cashmere and it is a bit of a faff removing them.
I have a cashmere jumper from M&S (about 5 years old) loads of bobbles and sheds fibres everywhere. Cannot be washed in biological washing powder/ liquid.
The merino wool £25 v neck jumper I bought from M&S about eight weeks ago washes beautifully and has not bobbled yet after twice weekly wearing and washing. It's the purple one and is a gorgeous colour! Will be buying another in a different colour soon, shame the colour range is limited though
The reason I have only just bought a cashmere jumper (apart from them being too expensive until recently) is that I don't think they are very child friendly. I would want to wash it as little as possible and you can't do that with little ones wiping their faces on your clothes and worse!
I'm right now wearing an expensive cashmere cardigan ruined by snotty noses, projectile baby vomit and crusty oatmeal. Be wiser, go with merino for the moment. In a year or two you can go back to cashmere and will perhaps have time to care for it, too.
Jax - puppies clearly have a thing for cashmere. Our pup chewed the collar on my roll neck cashmere sweater when it was laid out to dry. I hand stitched it using embroidery silk. It is barely noticeable but I wouldn't be able to wear it for smarter occasions unfortunately.
You can get rid of bobbling by using a knitwear shaver from John Lewis. Cheap and does the job quickly.
oh and to answer OP, I would probably go for the cashmere in this instance.