It depends on the idea you want to execute really. Illustrator is better with vector and Photoshop is better with bitmaps. If you just want straight up text that scales well, Illustrator is the way to go. If you want to add realistic effects like text that has grass growing all over it- Photoshop would be your best bet. If your images are turning out blurry in Illustrator you're either applying a blur effect or saving out at too low a resolution.