As per the title really. Whats peoples veiws on totally round peripheral ports compared to rectanguler ones?

 

I've never worked with them, but from enigeering point of view, they are easier for the DIY builder to make. A round hole will flow less total volume than a rectangular but once the the hole has been drilled, porting a round hole to a rectangular one isn't hard, depending on how the sleeve is installed. For high rpm engines, rounding the top/closing part of the port will put less stress on the apex seals.