SS is better than copper overall.

Copper is easier to work on. SS reduces heat lost vs copper

If it is PVC replace it with ss or copper since you have not tile it. When PVC get hot it is not about melting, it get soft and with water pressure it get pregnant. Not that it will burst. It wont burst embedded in concrete but the joint will leak. By then imagine you have to hack the whole and all the pipe out. Good luck.

Not really.

ss use copper compression fittings. Copper pipe you can bend and adjust, ss you can not bend easily as copper unless lenghty. And because both use compression its angle can be adjust by simply loosening and tighening. Also you can open the compression fitting and refit whenever there is an elbow. No need to cut and re join. All fittings can be reused except you got to get new rings, the copper rings at RM1 to RM1.50 a piece. The fittings of course is a bit more expensive. Tools to use the wrench and pipe cutter, that's all. No glue no Teflon tape. Teflon tape optional, just for smooth tightening not for waterproofing.

I cover all my copper pipe with insulation since you insisted last time. Previously have to wait 10 to 15 sec turn on full hot water for hot water to reach and come out. Now, no need to do so even after few hours someone come out of bathroom and I go in. Just turn the mixture on the usual center and in 3 sec warm water is out and no more adjust here and there. Also, the water seemed to be hotter now that I have to move more to the cold side. I think this is due to heat lost last time without insulation as the heat is transfer from solar hot tank via copper pipe to the bathroom and as air surrounding is cooler than the copper pipe and heat is lost from copper pipe to surrounding air. Thanks for your insistence. and believe

Sorry did not read properly.

Yes, PPR is better than ss reducing heat lost.

How?

OIC. Can that be cheaper than buying the aircond insulator? I bought at RM4 per piece. One piece is 6 feet long. I think that is a great idea when you want to insulated the pipe and conceal it in the concrete. The aircond one is so thick and if conceal with it in the concrete it will go too deep not only you have to connect a fitting to let it come out of the wall, it also make the wall weak occupying the wall space and make the concrete at that wall thin.