Which, if any, pass is best depends on your specific itinerary.  Since you don’t have an itinerary, it’s impossible to give good advice about railpasses.

Some things that may help you decide:

Rail travel is expensive in France, Germany, Benelux, Switzerland, Austria and Scandinavia.  If you’re doing much travel there, some kind of railpass will probably save you money.   If you think you’ll spend a lot of time in these countries something like a 10 day select pass in the 4 or 5 of these countries where you’re likely to take long trips will probably save you money.

A railpass is usually a toss-up in Italy and Spain.  There isn’t much of a rail system in Greece and bus is often as good a choice as the train in Ireland.

Rail travel is cheap in Eastern and Central Europe.  A railpass is a waste of money for most itineraries there.