i'm a lowly gold and a pretty big fan of the Conrad, if only because it's a much nicer property, and i don't really care about upgrades in tight international markets like Dublin.
plus, i believe the rooms are nicer in the Conrad, with the big honkin' caveat that i've stayed at the Hilton all of once and the Conrad enough times that i had staff members who knew me by name in the late 90s. i'm biased. but it's worth the $70 more, IMHO.