In general there are a number of different distinct workflows that lead to a poster. Each workflow has a number of software implementations.
- Word Processor (Word, Pages, OpenOffice Writer)
- Presentation Software (e.g., PowerPoint, Keynote, Impress)
- Vector Graphics (e.g., Illustrator, Inkscape, OpenOffice Draw)
- Desktop Publishing (e.g. Publisher, In Design)
- LaTeX
There are advatages/disadvatages to each category and to each piece of software within a category. For making a poster, the differences within a category are much smaller than the differences across categories.
Word processors are probbaly the weakest for layout, but are likely the software you are most familair with. Presentation software is a little stronger on the layout and also something you are likely familiar with. Vector graphic programs are really strong on the layout, but take a lot of fiddling. Most academic work doesn't require extensive use of a vector graphics program, so most people are not familiar. There is little added benefit of learning one. Desktop publishing software is really designed for making posters and other complicated layout (think magazines and brochures). There is almost no reason for most academics to master a desktop publishing software. LaTeX is an "oddball" you can use it for everything and it is well suited for both simple layouts and complicated layouts. The learning curve is pretty steep.