If you want to repair copper, you need to use a torc and solder. That’s not usually possible if the repairs are in difficult to reach places.

As a homeowner, I find copper to be pretty easy and approachable. Not only are torches cheap, they’re also good for a lot of things other than plumbing, so it’s totally worth owning one. Soldering really doesn’t take as much skill as people think it does, and has the advantage that it can be desoldered and re-soldered if it’s wrong. Also, all plumbing types are subject to the “difficult to reach places” issue; copper only stands out in the risk of setting something near the pipe on fire while soldering, and if you’ve got the minimum smarts necessary to put a wet rag behind it then it’s no big deal.

In comparison, PVC also requires few tools but has the disadvantage that, if you screw up gluing it, you’ve got to cut it out, throw it away and buy more pieces to start over. PEX seems like it’d be easy to work with (I haven’t actually tried this one yet), but depending on which proprietary connection style you go with, you need to buy weird specialized tools to stretch the end of the pipe and such.

Side note: some people might be inclined to use ‘sharkbite’ fittings to repair copper because they’re intimidated by soldering. Don’t! It’s not even really about the small risk of o-ring failure causing a leak in the future or the fact that sharkbite fittings cost more than soldered copper ones; it’s just that soldering is so downright easy that the difference in difficulty is trivial.

What sharkbite fittings are good for is temporarily capping off the end of a pipe when you want to be able to turn the water back on before you’re finished doing whatever you’re doing to it.