With a hashrate of 1 PH is best to use the proxy for submit share with high difficulties 500K and above or not use the proxy and have more connection for submit more share with a lower difficulty on average 70K.
From a latency point of view, ckproxy will mean much less network traffic between the proxy and the pool (if not run in passthrough mode)
since one work item will be sent each block change to ckproxy and the ckproxy will break it up to each local miner.
From a variance point of view, of course a 500K difficulty will mean higher variance than 70K difficulty.
However there is no average expected loss due to the higher variance, just ... higher variance.