I have used Microsoft PowerPoint to make posters so far, and I am considering giving Adobe Illustrator a shot for my next poster. What features does Adobe Illustrator lack compared to Microsoft PowerPoint to make a poster?
For example, one cannot generate bulleted lists automatically in Adobe Illustrator.
(I am aware of the question Software to use for creating posters for academic conferences?.)
I believe that Adobe Illustrator has many more features that MS PowerPoint for graphic design and image processing.
The key question is: what will you use those features to accomplish when creating your poster?
I created sever posters in MS PowerPoint and found that it had sufficient features and was easy to use. The only issues came when trying to print it out, because the output of Mac PowerPoint wasn't compatible with the Windows PowerPoint that the printer used.
In my view, extra-fancy graphic design will not result in better posters. Instead, what most posters need is bigger fonts, less text, bigger/simpler graphics and images, and headlines + call-outs that guide the viewer through the story. You can accomplish all these goals using PowerPoint.
So I haven't kept up with how illustrator has changed over the years, but when I used it regularly (10+ years ago), I did primarily because of its ability to make vector based graphics. I think (any one can correct me if they know better) that Power point has this ability, but not nearly to the extent that illustrator does. In my opinion, illustrator and power point are fundamentally different in what their intended uses are. Even back when I used illustrator extensively, I never used it for layout and design. I would import graphics from Illustrator into adobe Pagemaker (which is very similar to power point, and imo more appropriate for poster making).
I think it would be fairly frustrating to make a scientific poster solely in Illustrator.
Illustrator is nice for designing individual vector graphic elements (such as logos) but it is not for typesetting and page layouts. It will also probably be problematic when you try to combine graphics with paragraphs of text, like typical scientific poster. This is usually, what typesetting applications like InDesign do. InDesign can be used for a single page layout as well. On the other hand, if you do not know InDesign, it will probably be overkill to learn it for creating a single poster.
For scientific guys like me, with no artistic ability whatsoever, I found using latex / beamer with some existing poster templates the easier thing to do. It also has the advantage that you can copy text and formulas directly from your poster paper. So, I would strongly advice you to use beamer, since it is also what most scientific posters are usually done in CS conferences, judging from what I have seen in demo and poster sessions.
If you do not believe me, see this which is the most frequent poster design I have seen in conferences. It takes 2 minutes to do it in Beamer but it will take many days in either Illustrator or InDesign
My experience involves an unfortunate truth that I haven't seen mentioned in any of the other answers.
In many interactions with program managers here in the US, I need to create slides in PowerPoint because either 1) it is a required format for certain communications or 2) the program managers use PowerPoint to communicate elsewhere in the government and giving them PowerPoint slides makes it easier for them to include my work in their communications.
This, in turn, creates a significant network effect, because communication with program managers in proposals and reports often predates both papers, talks, and posters. PowerPoint thus has a major advantage over other software alternatives (including Adobe Illustrator), in that my graphics are already in PowerPoint and it's much easier to move them to different documents within the same program rather than shifting them between different programs.
