Copper pipes must be replaced. Minute holes developed in copper pipes over time lead to leaks, and millions of homes have no insurance once that sort of flood occurred.
Replacing all the copper in the home with plastic and sell the copper will make your a fortune.
The advantage of copper remains that it is rigid metal, and you can burn it without problem. Also it act as earth point for the electrical system in homes.
Copper can be replaced by CPVC and PEX. The other camp is PVC which is not copper compatible. PVC is usually found outside houses for the main supply, and for irrigation. PVC is not usually found inside houses as it cannot be used for hot water.
If your pipes are PVC, it does not make sense to change it to something else. Unless you need to connect to metal devices. I'm not sure what the code is, but screw them together is pretty easy and leak proof. But anyway, threads are trouble.
In the copper/CPVC/PEX camp, all can be connected with push fittings. CPVC is rigid, using glues, while PEX is flexible and uses clamps.
Almost certainly PEX is the material of choice whenever you can. You don't need angle couplings to go round corners. The total number of joints is less. With clamps you can use it immediately. If you don't want to invest in a good clamp for over $100, you can get push fittings at a few dollars each.
Measurements no longer need to be accurate, as long as the pipe is longer than what you wanted. For example, to replace a broken section of copper pipe or CPVC, you need to cut pipe to exact length and use unions to connect to the old pipes. For PEX you just need two adapters and a length of pipe longer than the bad section.
Soldering copper pipes need a lot of clearance from the sides, or else you need a soldering shield. Glues are best when you have little space to work with.
Push fit need to have clearance along the pipe to push things in, and to take it out.
Soldering and gluing are rigid joints while push fit couplings can be rotated freely. This could be a good or bad point. Ball valves with push fit ends are still able to rotate after you install it. You need two hands to operate the valve handle.
Threads are trouble but they are compact compared to other reusable push fittings. In practice, never assume that they are reusable. The threads are so easily damaged when you screw it back again. Often you can't even unscrew them apart in the first place.
Gatorbite vs Sharkbite
I used both but can't comment much other than that they works. Threads always start dripping at the beginning, but somehow hard water seals the threads.
When you put two devices with push fit together, you need to use a short pipe to connect the two. It's is bulky. I was too stupid to use too short a pipe, and I can't even put the disconnect tool in place. I saw the two apart. The good thing about Sharkbite is that no matter how short the pipe left alone inside the coupling, you can take it out with a nose pillar and some patient.