Well - Salix are similar in price.
Both are top end product. The Salix Pod 1 pads and gloves (and Pod Black gloves) are RRP of around £100/£70 (£100 for pads and £70 for gloves.) The Newbery Thruxton (£100/£65) and SPS (£110/£70) are the same kind of excellent quality!
The Thruxton have now introduced the impact gel technology but unless you play on a very bouncy wicket where the opposition bowlers are serving up some 90mph+ balls, then who knows how much the gel will be needed.
Let's just say that if the top of the range Salix and Newbery softs are not good enough for you, then good luck!
I would say that quality wise there would be little or nothing to choose between them. So I would try them on to see if either fit you better that the other, and if they all fit you well then maybe choose whichever colour and style you prefer!