tax is paid by the airline. It's in the contract. What you get on the contract is what you get. no deductions. Actually all expats here do pay tax. Everyone i know. teachers, lawyers doctors. Everyone. The contract states all taxes are paid by the company. In reality though you can't get any proof of this so if you need to show the tax office at home any hard evidence other than your contract, well you can't. A few pilots have been caught out by this. I think the canadians and americans inparticular.
upgrades are not dependant on the contract company. However i do know that PARC are helping their guys with the 15K bond. I'm not sure RAL are helping their guys at all.
We all got a 200 dollar payrise in May. Everyone. The PARC guys were paid this right from the get go. The RAL guys have been told that to get their raise thay will need to sign a 5 year contract. So the PARC chaps are now on more money. It's your choice who you sign with. I'm just passing on some useful ifo that may help you.