Sometimes you are forced to use a line bored case, this could be from financial reasons to time. Whatever the requirement, it is your choice to be responsible for and it is critical you know that it is unlikely to provide 100% life and will never stand up to any hard use. Treat it tenderly and it will give back the most it can.
When the case is only slightly worn and you want to line bore and reuse it, the #1 question will be, "Who is qualified to do it the correct way? Do they have the correct tools? How can I tell if they did it right if I don't have any precision tools?" Those are the $64,000.00 questions. Most shops use a simple electric drill (some use a lathe to feed the same tool) driven tool that centers on the pulley and seal holes. This is a poor way to be assured of a precision center. The pulley end will rarely be round and straight. The tool, which is inserted in both ends of the case, is bushed to allow the bar to turn. These bushings are fairly good when brand new. As they wear they get sloppy and allow the alignment to change and have no adjustment to them. These will determine whether your line bore is maintained in the same place or moved as well as what size it is.
When it is perfectly straight to the pulley, cam tunnel, and flywheel, all is great. However, most of the time it ends up out of alignment, then the gear size is way off, pulley and/or flywheel seal leakages show up after a few thousand miles. The one failure seldom connected to a line bore problem is wrist pin keeper failure. Because the crank is no longer lined up, the rod runs at an angle and pushes against the pin loading the keeper beyond its capabilities. All of these are undetectable with normal measuring equipment so it is really a gamble. When the case is mounted on its original (tooling) fixture pads to be line bored the chances of a proper line bore are much better, there are only a couple of these machines in the USA.
Now it gets down to the capability of the machinist. How close can he dial into the original center line and how close can his machinist perform the operation? How close can he set his tools? The message in all of this is buyer beware. Do not just listen to their story. Check out what they can do. Look over the equipment. What I do is have them tell me what they use for equipment and how they measure it for alignment to the cam, pulley, flywheel seal hole, and cylinder seating surfaces. If the answers do not support what has just been covered, just say "Thank you" and find someone else. Whatever you do, please do not use this information to make them wrong or you will get to hear their story on how they have done 250,000 cases this year and never had a failure, low oil pressure or overheating problems.