The St Michele is the $11 per glass sparkling wine that is covered by the SBP. We drank a lot of it our last two cruises. We like it. There is also a prosecco at $9/glass, that they use for Mimosas. It is definitely not taking the place of the Wycliff. The Wycliff is used for the large free pours, like the welcome aboard toast by the Captain, the Mariner's Reception, etc. The Wycliff is also used for other mixed drinks that have a sparkling wine in it.
To be honest, we drink a fair amount of champagne of a wide variety of qualities...we are even wine club members at Korbel Winery, one of the largest producers of sparkling wine in the world. Had two glasses of the Wycliff at the Mariners reception, and had a headache the rest of the day. That is reportedly caused by smaller bubbles in less expensive champagnes.