Pex of any sort is on the lower ranking side of plumbing if you wanted the "best" for say , longevity, or chemical resistance, or less chemical leeching, it has its place and use, but this is the easiest for the plumber to install in any situation, is it the right type of pipe for your situation? I dont have that info, but its not the best pipe to install imo. This is PEX A, its extremely flexible, and has its pros and cons, if you wanted the best of the best, you need to be more specific by what you mean by that with your plumber. If i wanted to replace all the plumbing in my home, I would go for something like flowguard gold CPVC just like you have there in the picture if I could afford it, if its a long term home, and i didnt plan on major renos down the line. I would choose CPVC due to its purity for potable water, rigidity, and longevity which can last double or more the time frame of PEX. Considering the circumstances here, I believe your plumber went with fast, cheap, and the install itself isnt the best install practices considering this junction area. Pipes expand, contract, and wiggle each time you turn a faucet on and off with or without the water hammer arresters, majorly less with them of course. Thats why I would choose something more rigid or properly route pipes without letting it lay across the edge of a piece of wood or any sharp edge. PEX A lets you go around just about anything inside the walls, so im seeing this as "the best" for the plumber to make quick cash out of quick work.