Housing in planned developments shall be permitted in R districts as follows:
(a) For development of land of two (2) acres or more.
(b) For development of land less than two (2) acre where such development is more appropriate and more efficient than conventional development because of environmentally sensitive areas, existing natural features or scenic assets, the amount of land available for infill development, or because of the age of existing development in the vicinity. (See Section 1129.05 for standards relating to developments of less than two (2) acres).