Large main line comes in to the manifold and to the water heater (an on demand unit) which also comes back to the manifold (there's a hot and cold side). The manifold in my case is within a foot of the water heater.
A home run in the proper sized pipe from the manifold to every outlet...so, for a bathroom, one cold line to the toilet, another to the sink faucet, yet another to the tub faucet. Two hot lines, one to the sink and one to the tub...and so on around the house.
The pipe is cheap and durable, so the extra lengths are not an issue. Come in red and blue too! You now have central valving instead of the little hidden ones under the sink that will twist off the first time you really need it LOL!
There are NO joints under the house or in the walls to ever leak.
Hot water reaches the target sooner because the line is only that...instead of running a 3/4 line to the bathroom with t's and splits (the volume of water in the 3/4 line is substantially higher than in an equal length 1/2 line).
Hot and cold stays balanced, even if somebody flushes the toilet whilst you're in the shower since there is no pressure drop on the the cold line right there at the toilet or whatnot...rather, any drop would be at the manifold and would be the same across both sides.
Gaining WIDE favor over copper and other systems, in cost, durability, and efficiency. I also like it because there's less chance of somebody burning my 100+ year old house down with a torch (annoyingly common). It's something like 1/20th the time to install.
Also resistent to freeze damage, corrosion, scale accumulation, etc...and...in my case...it lends itself to the incremental progress of our remodel. Get the mains and the water heater and the manifold in, and add "circuits" as needed.
Anyway, code approved in my area for domestic water supply is only copper or PEX. I've done houses in copper. For mine I'm going with the PEX.
