Standard "drain" & "return" lines are usually 1" for drain & 3/4" for return.
Of course, the larger the tank volume, the more we lean towards larger hole ratios.
Currently on my 120gal I have 1 & 1/4" drain and 1" return.
However if I had to start from scratch, I would probably go back to the standard 1" drain & 3/4" return(mostly because return pumps are typically 1/2" or 3/4" outlets).