Having returned to the hobby recently I have started to visit various exibitions, mainly for ideas and inspiration. The layouts that have attracted my attention the most have tended to be the smaller type. This is usually because they have great detail and realism with a feeling that you could almost be at the lineside. Having said that a degree of operational interest is vital if it is to retain my interest beyond the initial "wow" factor. The ongoing saga of layouts with absolutely nothing happening on them for minutes at a time is a common complaint from visiters to exibitions. Operational realism at home, the club and with like minded friends is fine but is not really a crowd puller at exibitions. Most people do like to see something happening, so your idea of standard gauge and narrow gauge should allow that. Good luck!