Ideally don't use any of them but if you have to then the best of a bad lot seems to be Scanlan & associates.
McNamara's will spend their time trying to sell you insurance products and giving you f**k all advice for the money you pay them...in fact an example of that is last December they sent an email to all the pilots advising that the new budget was just out and for the 'reduced sum of 100 Euro plus VAT they kindly give the pilot advice on how to reduce his/her tax liabilities!! (thats in addition to the 3% plus VAT they already receive).
CXC do nothing...know of a guy who hired a car for work ex base and took the insurance and they wouldnt allow him to claim it as it's an 'optional' extra. There are a number of allowable expenses that the revenue allow you to claim for but that CXC have a different opinion on.