Basic difference between a Snap T and a Circle is what you do with the rod tip AT THE END. Both start the same way, high rod tip sweep with a over/under pass with the rod tip. Where they differ is the Circle sweep keeps going past you; the Snap T is a rod tip 'chop' back down on the water in front of you to set up the anchor. Edit to add a bit: With a 'circle' its not unusual (lots of line out the tip-top) to have the anchor set up well above you ... and you just wait for the thing to 'float by' then into the D loop/forward cast. I actually had one time (lot of line out) where I had time to pull out/light a smoke!) while the line did its thing. With the snap T the anchor will usually set up where you want same or slightly down stream. Where the 'danger' comes into this is where's the fly going to go? With a circle highly unlikely your rod will be put at risk. Not so with a snap t ... which why its also called the 'Snapped Tip.'