In my opinion, drawing in Photoshop takes a little "getting used to" compared to Illustrator. I do, however, prefer Photoshop over Illustrator since I am a genetically artistic and can incorporate photographs of my own fine art work into my computer art.
If you have free time, click the link below to find tutorials on both programs. The tutorials are availble all over the internet, but I really like this one. You can look through some of the tutorials for "effects" to see what fits your own personal style. Then, by looking at what others have created, you can decide which one to buy. They are both excellent programs but if you aren't looking to make a career out of graphic design you will need to decide which program has the biggest potential to benefit your own, natural style-it will more than likely be Photoshop.