Here are a few things you might want to consider.
- Rigid sole - A shoe with a more rigid/stiffer sole will allow you to transfer power to the pedals/cranks with less loss due to flex. However also weigh in the pros and cons as this will generally make them less walkable. Some shoes use carbon fibre soles to make them as stiff as possible.
- Quality of construction - Good stitching and quality materials so they don't fall apart easily. Good shoes can last 10 or more years.
- Adjustability - Better more expensive shoes generally have more securing points... three vs one or two straps and some may have micro-adustable buckles in lieu of velcro. Cheaper shoes generally use laces.
- Weight - The lighter the shoe, the less weight you're having to drag around in circles.
- Reflectivity - Many cycling shoes are made of some sort of reflective material. This can help in low light cycling conditions to make you more visible. Since your feet will be moving, it becomes more apparent to the human eye.