The most important advise I can offer if the type of timber that is used in the manufacturing of your windows, it is important that they are hardwood as unfortunately Ireland is not really suited to softwood due to the damp atmosphere that we have compared to our continental comrades.
The type of Hardwood should ideally be Iroko as this has the highest durability for our weather conditions. Mahoganny only had a moderate durability tag attached. Once in a lifetime is enough to be investing in expensive windows and doors, without having to replace them in 10 to 15 years time.
In a previous thread I have posted the actual durability details of the Hardwoods that come into Ireland.
As to the weights or spiral balances, it is down to personal choice as neither give any trouble.