I was at Slane 1 and Croke 1. IMHO Slane 1 was a better overall experience. (Make no mistake, Croke 1 was unbelievable too and I'm extremely lucky to have got a ticket !!!)
Remember, it was the day after Bob Hewson's funeral, the sun was shining, Coldplay and Chili Peppers got the crowd to fever pitch before U2 entered. U2 played a blinding set (inc Sort of Homecoming, Bad, etc). As Willie wrote in the notes to Slane DVD, that at Slane 1 it was the first time he had seen the band fallover and the crowd picked them up (he makes note that this is usually the other way around).
So having seen them 24 times (every tour since UF in 1984), Slane 1 will take some beating ...
Roll on Europe 2006 ???????????????