Just to clarify the nomenclature a little:
First and foremost, there is no VERSUS. HOn30 and standard HO are both built to the same scale, and can happily co-exist on the same layout.
HO scale, 3.5mm = 1 foot, or a scale reduction of 87.1:1. This applies to models of everything from the Petronus Towers to fireplugs.
Standard gauge - 56.5 inches, the most commonly used track gauge in North America.
'HO Gauge' usually refers to track laid to a gauge of 16.5mm, which is within 0.025 inch of being correct for standard gauge in HO scale.
30 inch (or 762mm) gauge. Use of this gauge by prototype rail lines was uncommon in the United States but considerably more common in other countries.
HOn30 (or HOn762, HOe, HOn2 1/2) refers to building HO scale models of equipment which runs on 9mm gauge (which is N-scale standard gauge) track.
HOn762 is very popular in Japan, where it is used to model the wide array of 762mm gauge railways that once existed there. Almost every issue of Tetsudo Mokei Shumi carries coverage of somebody's hyper-detailed layout (which is usually about the size of a place mat...) Themes range from logging and industrial lines to suburban EMU service.
Chuck (Modeling Central Japan in September, 1964 - with two very different 762mm gauge feeder lines)