I've never used Newtones; although I think I might have done once and they came off faster than they went on - but I suspect that they were made by a former incarnation of the company

Much as I hate to disagree with Dave H, I suggest that you check out the price of both for yourself. Yes, D'Addario can be expensive if you go into a music shop in the high street (are there any of those left!) but you can buy them on line for much the same as Newtone sell them direct (try Strings Direct).

If you're prepared to import them yourself, as I prefer, the price really tumbles - although you have to factor in shipping, duty and other iniquitous charges + you need to be ordering at least half a dozen sets at a time.