From what I've read, AUCTeX (which is also an Emacs extension) is better for writing full-blown LaTeX documents. But yes, the preview functionality in both is a

From what I've read, AUCTeX (which is also an Emacs extension) is better for writing full-blown LaTeX documents. But yes, the preview functionality in both is a big improvement on directly viewing the source markup, and if I couldn't use LyX then I would certainly use one of those instead. In fact LyX also supports instant previews of equations. That might sound a bit odd since it already displays equations graphically, but it's nice to see a pixel-perfect display of them. It also supports wrapping instant preview of arbitrary bits of the documents, which is really handy when you have inserted explicit LaTeX e.g. a Tikz diagram.