Manifold for PEX water runs

Say I want to re-do my plumbing from Copper to PEX....I see there are those manifolds that would allow me to run several independent runs to various rooms unlike the current setup which is simply a series of Tees and splits.... Are there any advantages to running cold water via PEX tubing from the manifold vs. following the existing paths ? Currently Copper 3/4 before Boiler and then all water goes via 1/2 pipes. I would do the same sizing with PEX thanks!