is there something significant I can do in LATEX/TEX that I can't do in Mathematica?
- far better at handling print page layout … for example, 2 column layout, or page breaks, footnotes etc
- some journals/conferences require submissions in LaTeX format
- I am sure there are other benefits!
— but much steeper learning curve … though I believe nice front-ends exist (is Scientific Word still around?)
- typesetting is easy (palette graphical entry, keyboard shortcuts, WYSIWYG etc)
- everything in-built - including beautiful mathematical fonts
- output to either pdf, or mma notebooks (which can be read for free on any computer, or through a web browser using the CDF plugin (Computable Document Format).
- can export individual equations to LaTeX: [ I use this sometimes to paste output here at math.SE, and it works quite neatly, but sometimes it needs a manual tweak, for example to decide what goes into fractions, and what lies outside the fraction ]
- can also be enormously powerful and flexible like LaTeX [though this does require knowledge or tweaking with lots of typesetting options]
Both LaTeX and Mma use style-sheets, and use plain text file formats (not binaries) which can be opened in any text editor, and even edited, if so desired (though not necessarily for the faint hearted).
Having co-authored/typeset a 500 page Springer book in Mathematica itself (with output to PDF for the printed book version) … I can say that getting page layouts to be aesthetically pleasing was a VERY difficult and VERY time-consuming task. At the time, I complained bitterly to Theo Gray who was head of user interface design etc at Wolfram … and I suspect that my complaints mostly fell on deaf ears :) Theo Gray was rather forward-looking, and I believe he was just not interested to expend the effort to bring old-school printed page-layout tools to Mathematica (footnotes, columns, proper WYSIWYG page layout etc), … to an evolving world which he clearly saw as moving away from old-skool print and towards live/interactive/virtual/scrolling etc.
Maybe he was right … but doing printed output in Mathematica is still a pain. And I also think that explains Mathematica's focus in moving towards live Computable Documents (live documents where the equations / diagrams etc are live and interactive).
Open-source vs Commercial
The OP specifically noted that he already had Mma, and so price was not a relevant issue for him. I don’t particularly care whether the software I use is open-source or commercial … although, obviously, like everyone else, I prefer getting stuff for free. But on balance, I also try to use the best tool for the job. And if I am going to use it a lot, as long as the price is not unreasonable, … well, one ultimately has to put a value on one’s time, and place the appropriate respect onto what one does. Maybe walking is cheaper than driving, but it is not always the most efficient solution.
As to longevity, I frankly don’t see any evidence that open-source platforms survive any more robustly than commercial platforms. In fact, the suggestion that people should not use a commercial platform such as Mac or Windows or Photoshop or Autocad or iTunes, because one day it may not exist … seems as far-fetched and extreme as those who don’t want to get out of bed in the morning because one day the universe may no longer exist. I prefer to live in the present, and I try to use the best tools that exist in the present.
Microsoft Word is great and has huge market share. Before Word there was Word Perfect, that was great and had huge market share. Before Word Perfect there was Word Star, that was great and had huge market share.
Moreover, the biblical proclamations of extinction and sudden death are just not the way the world operates. It evolves and we evolve with it. I cannot think of any new major platform that has supplanted the past, without taking the past with it. MS Word might have supplanted Word Perfect and MacWrite, but you can be sure that MS Word was able to read all those old MacWrite and WordPerfect files. New Macs with Intel processors succeeded because they could read and run the files from older Macs with Motorola processors. Windows succeeded because it could read MS-DOS. No doom and gloom … just evolution to something (hopefully) better.