'We decided to play in Lansdowne Road because we believe we can get the biggest provincial attendance in the history of Irish rugby," said Williams.
"Donnybrook, much as we love it, cannot properly host a match of this magnitude yet Lansdowne Road provides us with an advantage - the support, the Saturday, the surface, our skills."
Leinster have seen interest in their quarter-final match mushroom in recent days, and Williams and his side are experiencing life under the public spotlight.
'Our Open Training Day last Sunday had close on 2,000 young fans here with their parents; many have never been to a Friday night game."
And Leinster have taken the decision to switch from their spiritual home to accommodate the extra supporters who are desperate to see the action.
'We salute the fans who support us in Donnybrook, they are on the wet and windy terraces giving us their fantastic backing.
"We are now in a position to accommodate all our loyal fans and also to, at last, give many more fans the opportunity to see and support Leinster, the number one ranked team in the Heineken Cup after the pool stages.
"We have sold 11,500 Leinster jerseys this season - not even half could hope to be seen in Donnybrook. A Heineken Cup quarter-final in Lansdowne Road will enable all our fans from Dundalk to New Ross to see the match in comfort."
Leinster have a good record at the famous Dublin stadium, and Williams will hope his side follow up the success of the past on April 12.
"We won the Celtic League with 3 play-off wins in Lansdowne Road -we have no fear of a bigger ground.'
Leinster's Chief Executive Mick Dawson confirmed that the goal is to get as many Leinster fans into Lansdowne Road to support the Leinster team.'The ticketing arrangements will be finalised in the coming weeks but tickets will be on sale the week of February 24, online, through Leinster's clubs and schools and many retail outlets. Season ticket holders will receive priority booking.'