The integrated flux density distribution of clusters found in SZ surveys depends on cosmology and redshift. At redshifts below 1, an open CMD and a Lambda CMD model cannot be distinguished. At higher z however, the counts differ strongly.
The APEX SZ survey -even to a conservative detection limit of 150 micro K, corresponding to 3 mJy at 150 GHz, would for the unfavourable lambda cosmology find about 1 cluster per square degree at z>1, and one per 100 sq. deg above z=2.
Given the steepness of the cluster brightness distribution at high z, even a 100 sq. deg APEX SZ survey would find more high-z clusters than the nearly full sky Planck survey, which has a detection limit of ca. 30 mJy at 353 GHz - the Planck band with the highest resolution (5 arcmin).