I have used both Sharkbites and have done tons of soldering over the years. My preference is soldering because once it is completed it stays that way. Also, once you get skilled at soldering, you can do it well the first time every time. With Sharkbites, I have not personally seen one leak long after it was installed but I have seen several leak immediately after install because they didn't get quite all the way on or the pipe end was slightly elongated, etc. I think they have their place in everybody's tool box but I would never bury one in a wall or put it someplace where I can't see it readily to determine it isn't leaking. Another thing I love about soldering is that the connections themselves cost pennies compared to sharkbite fittings. I have two bags, one of elbows and one of splices that cost me about one sharkbite fitting costs. Yes you do need a soldering torch but I use mine for other things around the home so it isn't wasted money.
If this is a new leak, it may not be the joint that is leaking. Copper over many decades can develop pinholes, especially at elbows and other joints. If it were me, I would cut away the elbow and solder a new one in. They make close quarters cutting rings for copper pipe and I've never been in a situation where once you make one cut, you couldn't flex the pipe enough to get the ring on it and make the cut in the tight location. Another thing to consider with elbows, is that since you are removing the elbow you are removing some of the pipe length and that has to be replaced by either pulling one of the two ends of the pipe closer to the other or if unable, to splice in a longer piece of pipe somewhere along the line where convenient.
