Calling the MM300 a wannabe Rolex Sub is quite funny and not something I would expect from someone that handled both and knows a thing or two about watches (yes I know, both have black dials, a date at three and the hour markers are round :)). The heritage, the movement, the monocoque case, the lume on the Marinemaster 300 brush aside most boutique divers, including the AD and the Stowa.
IMHO, the MM300 competes with the Omega PO and the Rolex Sub. Testament to this statement are the large number of threads comparing these particular dive watches. I consider the Aquadive and the Stowa competitors for the Sumo at best.