Actually what's the benefit of paircoil compared to the traditional ?

Yours is a condo unit?

If its landed, i would advice to avoid internal water piping as much as possible, if it must be in the wall, use a removal panel/tile system...

Cause down the road you will definitely have water leakages... the hacking involved will bring tears to your eyes..

understood the difficulties.

My next place I will be re-routing everything to external. For those internal ones... all the joints will have removable panels, cause majority of the leakages are at the joints, pipes hardly break.