I have some of the following sets...
O gauge (1:47 scale)
S gauge sets (1:64 scale)
Some HO gauge sets (1:87 scale)
And some Z gauge sets (1:220 scale)
I really like the S gauge most of all. Large enough for full detail but not as bulky as the O gauge sets. Besides, O gauge mostly just looks like a toy version while S gauge looks a lot like the real thing.
HO just lacks the finer details I want to help believe it’s the real thing.
Z gauge is just a cute little thing pretending to be a real train...fun, but that’s all.