Moving overseas is expensive. Transportation alone can cost a few thousand. Then you would need to pay for packing and unpacking, insurance, storage, customs duty and taxes, there are visa fees and lawyer fees in some cases. A substantial part of the entire transportation may be via sea or air, depending on the mode you choose. This often propels some people to consider hiring shipping companies instead of international movers. Shipping companies would actually charge you a little less than what international movers would quote in most cases. However, you should not hire shipping companies.
There is a huge difference between the goods you would need moved and the freight that shipping companies usually deal with. Most shipping companies have expertise in handling large consignments. The cargo is mostly commodities. The consignments are shipped on an industrial scale and there is rarely any mishmash of different items in a particular container or consignment. There could be scores of containers transporting any one item in bulk. This is not what you need while moving overseas. Your cargo will be a mixed bag. There can be sturdy furniture and valuable gadgets. There can be fragile appliances and hardy tools. A mixed bag such as this will always require specific expertise.
International movers do not charge you only for the transport. It is a holistic service, taking care of everything from packing to delivering the goods and helping you to set up the various fixtures. International movers usually deal with customs and other legalities. Shipping companies can also deal with customs but they would not help you with anything before the goods are shipped and after they are delivered at your new address. In other words, the service is strictly limited to transportation.
Shipping companies dealing in freight do not have the bandwidth or the policy to entertain specific requests you may have. No matter how many items you need moved, it would never be the bulk that shipping companies deal with every day. Hence, a bulk rate or the actual cost benefit is not realisable. The lack of personalisation will have a serious repercussion as it increases the risk factors. The large containers that are usually packed with commodities are designed for that very purpose and the items shipped on a mass scale will be packaged accordingly. None of these factors will be suitable for personal items. Even though international movers may ask for a marginally higher fee, you must not opt for shipping companies. The latter will inevitably complicate your entire moving experience and it may eventually prove to be much costlier.