Glenveagh Properties has received fast-track planning approval for a 463-unit development in the heart of Citywest, Dublin.
But plans by Ironborn Real Estate to build 444 apartments in the south Co Dublin suburb of Stepaside have been rejected by An Bord Pleanála.
Glenveagh, one of the country's biggest builders, acquired the 7.4-hectare site at the junction of Citywest Road and Magna Drive two years ago.
Planners approved with only minor revisions Glenveagh's design envisioning 353 apartments in seven blocks mostly six storeys high. Most will be two-bedroom units.
The development plan also calls for 89 houses - 51 two bed, 20 three bed and 18 four bed - and 21 duplex units with two or three bedrooms.
In a separate ruling, An Bord Pleanála rejected Ironborn's plans for Stepaside citing several shortcomings, particularly concerns over the potential for flooding.
Planners cited its poor layout and design and the inadequate capacity of the local wastewater network.
Ironborn Real Estate had sought fast-track approval for its plans to build 444 apartments and a crèche on the 2.8-hectare site at Aiken's Village in Stepaside. The apartments would have been spread across nine blocks ranging from two to eight storeys.
But planners described the layout and design as poor, and expressed concerns that the local wastewater network lacked sufficient capacity for the development. This issue, they warned, could increase the risk of flooding in the area.
It said Ironborn's plans also failed to meet Government guidelines on sustainable residential development in urban areas in relation to connections and inclusivity.
The arrangement of the apartment blocks, it said, decreased the availability of attractive routes for pedestrians and cyclists.
The main public open space was also regarded as "not readily accessible".
The board said there was a "sub-optimal" distance between some buildings, while the positioning of some blocks failed "to ensure high-quality living environments" due to a lack of sunlight for some single-aspect units.
In its submission, Ironborn said it had received confirmation from Irish Water of sufficient capacity in the local wastewater network.
Dún Laoghaire-Rathdown County Council also had called for planning permission to be refused citing the development's height, design and lack of community facilities.
The local Belarmine Residents' Association said the apartment blocks, if built, would be out of character with neighbouring properties.
A majority of the 65 submissions expressed concern about the proposed development's potential impact on local traffic, which is already congested.
Most submissions complained that Stepaside did not have enough school spaces, childcare facilities or doctors' surgeries in the area to support the existing population, never mind many hundreds of new residents.
A planning board inspector had recommended that plans to provide 455 car parking spaces should be significantly reduced.