I've always also liked the sleek looking Winchester M100 semi-auto rifle. With it's one piece stock it definitely has a different appearance than say a Remington M742 from the same era. I've always liked this semi-auto rifle that is stocked more like a bolt gun. The long one piece stock gives it a distinctly more classic look, in my opinion.
As with other Winchesters of this era, there were some changes with the M100 come 1964. As with the M88, however, the M100's changes were pretty minor and pretty much restricted to a new checkering design on the stock.
The M100 seems a bit more popular than the M88, but perhaps the owners of the M88s just cling more dearly to them. The M100 certainly seems to be found for sale more often than their lever counterparts. They were available in similar chamberings as the M88; .243, .284 and .308. The .358 was never chambered in the M100.
As with the M88, the M100 was made in two styles, the rifle with it's 22" barrel and carbine with 19" barrel. As with it's sister M88, the M100 carbines are much more rare and worth considerably more today. The carbine was made for fewer years and in much smaller numbers than the rifle model.
One last comment on the M100. Winchester has had a recall for these rifles for many years, something to do with the firing pins and the possibility of misfires or double firing. If you google Winchester M100 recall, you should find the information you might need as a M100 owner.