FWIW - In my experience it is irrelevant whether it is students or professionals. I have let the rooms in the house I live in for the past 4 years and there is no strong preference to either one.
It really comes down to the person and how much they respect other people's property. A professional / ord. worker can create just as much damage / abuse to your items as a student can.
How do they keep themselves? Do you get a good vibe from them? I have learnt the hard way and now between me and one other person in the house, we decide who comes in. I would welcome a second opinion from a close mate / family member when you are showing prospective tenants around.
If you feel you must get a higher deposit by all means do this if it makes you feel more secure. However, a person will always do what they want to do.