LBurford, parafilm is the best for small grafting, and it is not hard to have a successful graft. Parafilm is not rigid, but it is slightly stretchable. The pros would be its ability to seal the graft tightly with little effort, and the cons would be its undurability and very high cost.
If you are grafting on big scionwood or rootstocks, parafilm would be a waste. For bark graft on medium to large branches plastic wrap is preferred; however, it is not recommended to overtighten the graft union. Those un-professional grafters on youtube tried to overtighten the graft uinons on their trees with hope that it would prevent graft unions from being swollen. We could avoid the swollen graft union using our skills and experiences, and it also depends on several factors; however, it is not neccesary because a swollen graft union will finally disappear in a few years unless the graft is failed gradually.