I see where Rick mentions the choice between basic and super CDW (on pp. 567-568, RS Ireland 2018), but I can’t tell whether or not he recommends the more expensive option. What advice do any of you have on this? Thanks.
Not have that book nor have I rented a car in Ireland. In Italy 'basic' CDW limits your responsibility for damage to the rental car to $3000 or less ( depends on the rental car company) and "super" CDW reduces your risk to zero.
Read the fine print of whatever site you are looking at.
Which coverage you choose is up to you, based on your risk tolerance and budget.
Part or your decision will be based on the actual rates that you find available. While that section talks about how high the deductible can be, maybe you'd luck out with a smaller deductible, like €500. But given the number of unfamiliar situations you may face driving on the other side, many of us would choose maximum coverage. If you're able to choose that in advance, it may be a better value than adding it at the time of pick up - AutoEurope.com usually has that option or www.dan-dooley.ie is a recommended source for Ireland specifically.
And make sure you completely understand what each type of insurance covers. CDW and Super CDW covers collision damage. That's it no more than that. In other words, if you don't run into something, that insurance doesn't help. If you want vandalism and other coverage, that is separate. Tyres and glass is also separate coverage. It can add up.