A BGA component only needs replacing if defective, bad joints can be reballed. So if people have had success reflowing that model, then a new replacement may not be required.
Typically a professional repair will use new components, do the job once for it to work first time and be reliable. If repairing for someone else and it's secondhand parts, reballed or a reflow is ok as long as they know it's a temporary fix. It should be priced and discussed accordingly.
If you are repairing it for yourself do whatever you like, if careful you can reflow it and then later reball, several times even. Unless you are confidant with fine work I recommend that you practice on some old boards first, if you don't pay attention to detail you will just waste your time/money and do more damage.