Thin Albert you are a glutton for punishment, but you do ask good questions. I can't do your tax for you, but the tax rates in Ireland are lower than in mainland Europe. So too are social payments. HOWEVER, if you are then based at one of the continental bases and you or your family get ill - some important questions and issues begin to arise.
For example, did anyone tell you that Ryanair just cancelled, with a few days notice, Loss of Licence insurance? That's it. Just gone. You pay now (so now most probably will forget about LOL).
Bottom line: all of this is designed to get cash into your hands, to make your earnings look high and make you feel well off. The problems arise later. This is all smoke and mirrors - just like the "5 on 4 off". Now you have no insurance from your company, low welfare payments and problems if your real payment rate becomes known in one of the countries that provides REAL health care. And that is not to even get into the taxation "arrangements" that you might be responsible for sorting out should the tax authorities in another country come after you.
In any case, as has been repeatedly said above, what Ryanair say / promise and what they actually do is different. They are taking money from their staff all the time, with new "arrangements" or new "interpretations" of contracts. So far there is no sign that they will stop.
Equally, so far there is no sign that quite a large number of pilots will ever learn .... and so we keep meeting pilots complaining about months without pay, or contracts ignored. You can feel sorry for them as individuals, but as a group it is harder to be sympathetic. It must be said that there have been more than enough warnings here for the last year for anyone with a bit of wit to realise that something is not right. Get everything in writing - and in advance - though they will still tell you that certain things in the contract were "a mistake" and do not apply to you. When that happens, are you going to accept it? Most people do. And Ryanair know that. Which is why it will go on happening.