There are 3 types of yeast extract in NZ/Australia - Vegemite, Marmite and Promite. They're basically all the same in that they are all extremely salty tasting. BUT....

Marmite is sweeter than Vegemite

Promite is sweeter then Marmite

Vegemite: ( Kraft General Foods NZ Ltd )
Yeast extract, salt, malt extract, colour (caramel),
vegetable flavours, vitamins (niacin, thiamine, riboflavin)

Marmite: ( Sanatarium Health Food Company, NZ )
Yeast, sugar, salt, wheatgerm extract, mineral salt (508)
colour(caramel), herbs, spices, vitamins (niacin, thiamin,riboflavin)

Promite: ( Masterfoods of Australia )
Vegetable protein extract, sugar, yeast, natural colour(caramel) salt, thickener (Wheat starch), emulsifier (Glycerol monostearate) spices, added vitamins, water

The difference between Vegemite and Marmite is that marmite has a more caramel taste. Vegemite eaters will usually eat Marmite, but Marmite eaters may tend not to like Vegemite. Promite is just Disgusting!