Yeah, the ibex planes have a rounded bottom. This is the one I just got http://www.leevalley.com/wood/page.aspx?c=...amp;cat=1,41182 Letter B (the curved one). Haven't gotten to use it yet, but yeah, it looks to be very good quality, like the rest of their stuff.
As far as advantages or disadvantages, if you like using planes go with the plane, if you like using chisels and the like, go with the gouge, that's really all I can say. Oh, the gouge will take off more at a time, whether that's good or bad, but they can take off pretty much however much material you want.