I only know how to use (beginner-mode) Photoshop. Why is Illustrator better for creating logos, banners, etc?
Illustrator is vector based graphic program. Since vectors can be made to fit at anyy dimmensions that's is considered a plus , however my dear countryman do now this Illustrator is tough to learn (nashparliu) and even tougher to use to achieve the same results as Photoshop . To put it in a simple way it's 10x to 20x faster to use Photoshop rather then illustrator for a large number of things .
Photoshop for quick'n'dirty screen/web based stuff, and Illustrator for real world stuff (printing, tshirts, future/size proofing). Illustrator is the proper way to design logos. Anything created in Illustrator can be scaled up for billboards etc. If you're doing corporate work, or making logos for people that will need real world printing done, then Illustrator is the safest way to do it. Photoshop is fine for creating logos that are going to be web only. If you can, do your work at 300/600dpi, so you can get business cards and other smallish things printed if you need to. If you're making web banners for a specific pixel size, use Photoshop.
Photoshop and Illustrator are two different programs that offer very different things. Photoshop is mainly for photo manipulation but you can also do some drawing on it but it is not as good as Illustrator. Illustrator is a vector based program which allows you to draw vector items. Vector is math based and will basically allow you more freedom if you are going to create something that will need to be various sizes since vector shapes are 'math' based you won't have problems with things being pixelated when they are made larger
Actually when it come to t-shirts you're quite fine with Photoshop as well , you just have to be careful not to go crazy with the special effects . In fact the t-shirt industry has the best software in the shape of Photoshop plug-ins .
I'd say Illustrator indeed has a steeper learning curve than Photoshop. But they have different purposes, even if some of their functions overlap. Like the name suggests, Photoshop is great for manipulating and adjusting photos and graphics. But Illustrator allows you to conveniently modify and adjust shapes. You can do a heck of a lot if you learn to use them in tandem. If the need arises, I'll modify an element of a design in Photoshop, then import it into my design in Illustrator. For example, I like to make customized birthday cards for my friends. I'll grab images off the web, take out/adjust the parts I want using Photoshop, then arrange all the parts using Illustrator.
if you are creating logos or banners.. .you should vector based softwares in order to have quality images.. .what i mean is that images that are not pixelated when you try to enlarge the image.. .AI and Corel are great at that.. .although PS can also generate that but for me, i only use them to edit photos.. .