If you guys are into vector based designs then I would suggest adobe illustrator as the best creative tool out there in the market. Personally, I have created numerous medical illustrations for different textbooks for marketing purposes and it turns out this source has a lot to offer if you master the skill to use it. The basic problem encountered by every first timer is to achieve enough skill to work comfortably with the pen tool. Once you achieve that you can easily maneuver around and create whatever design pops up in your head. It's an easy skill to learn and there are numerous tutorials available online on Youtube that can direct you towards the right direction.
Therefore check it out if you guys have never tried it out before!!!