Would you recommend using Photoshop for designing professional event posters?

Illustrator is much better, illustrator uses vector, photoshop is more on pixel, high resolution will kill photoshop, printing companies prefers artwork made using Illustrator

Illustrator est beaucoup mieux, l'illustrateur utilise le vecteur, photoshop est plus sur le pixel, la haute résolution va tuer photoshop, les entreprises d'impression préfèrent les illustrations réalisées à l'aide d'Illustrator

Yes, of course, from my point of view Photoshop is the best in designing any poster, because of the freedom of movement and its multiple options, especially after the emergence of the latest version

yea u can but i will suggest illustrator

the effects in photoshop is more and better for making posters, but it also depends is the contents you want to put in the poster.

if there are images I guess photoshop is better, if not I think illustrator is better.

Photoshop is best option to design event poster if you are well familiar with it.poster can be made more interesting and outstanding using Photoshop application than anyother software

I agree on all answers of the experts here... 

for event posters i blindly recommend Illustrator for easy to work in vector basis as well as image which is very suitable for posters & other print medias

Yes but its not the only software that should be used in making a poster. Illustrator is also another software that is used in designing one.

Photoshop is used to edit photos as the very name indicates. It is not a designing software. You can use either Adobe Illustrator  or CorelDraw which I prefer more. Both of the software are vector drawing softwares  used in Graphic Design industry. The other option is (if you are not skilled in these) is to hire me. I am a professional graphic designer. You can message me here at bayt. Regards.

If you are perfect and all the things can make or adjust in Photoshop and it will fit in all requirements then ok. Otherwise you have to get help from any vector based software i.e. Illustrator, Corel Draw etc.

Moreover the vector can be enlarge in any scale but raster based image or design cannot be used in large sizes.