advantages and disadbantages of wholly owned and charter ship?

Answer 1

ad- You're free to use it anytime you like. No reservation paperwork needed. Your the boss. You can go anywhere you like.
dis- Fuel cost, dock fees, upkeep, maintenance, insurance, liability, depreciation, crew cost

Answer 2

That's a bit like asking the advantages and disadvantages of owning a back hoe/tractor vs renting one.
If you own the equipment it's yours; through the good and the bad, the ups and the downs of the market. (The marine industry is cyclical - there will be ups - when you can make tons of money, and downs - when you may actually "stack" your ship - because your profit would be negative if you operated.)
Additionally, all the maintenance is the owner's responsibility. This ranges from the typical routine replacement of consumable parts and changing of oil to the major special survey (typically requiring a dry docking) that has to be done every five years.
If you lease the ship you are subject to the whims of the market as well - during "good times" a charterer will have to pay top dollar for a ship; and may not have his choice of vessels, or have to wait until an appropriate vessel becomes available. However, when the market is in the "trough" of the cycle a charterer can get dirt cheap rates.
The owner gets to write off the depreciation of the vessel as a tax benefit. A charter does not.

However; in US waters most large operators see liability as the biggest pro/con of owning vs. leasing. According to US law, the owner of the CARGO is responsible for any environmental impact (due to an accident) on coastal waterways. This means that if you charter a ship (usually you charter the ship and crew together) a third party is moving your cargo (let's say oil). If that ship leaks or spills (or runs aground a la' Valdez) the owner of the cargo can be held liable. Under OPA 90 (the act passed after the Valdez incident) US companies operating in US waters have UNLIMITED liability - which means they can continued to be sued for unlimited amounts until a judge finally puts his foot down.

On inland waterways the operator is responsible for any environmental impact as a result of a spill or leak.

This is one of the reasons ExxonMobil's shipping company (SeaRiver) sold off their inland fleet of tugs & barges, but continues to operate the ships on their west coast (Alaska to the lower 48) run.