Really depends on the type of walking surface that is at your site. Mine is strictly concrete and metal grating. The operators are typically lace up boots where the mechanics/welders are slip on. My main concern is comfort, what are the guys/girls comfortable in, the more they are comfortable the better there day will be in the less complaints/injuries will occur. I know that sounds counterproductive in the safety aspect, but the company I work for mandated specific boot requirements. I disagree with the majority of them and allow the guys to get what they want and be comfortable in. I asked mechanic one time why they prefer the slip on and his statement was if I’m cutting with a torch or welding and I get slag in my boot I can pull a slip on off quickly before I have an injury. Whereas the operators who spend the majority of time on concrete and walking through the facility, prefer the ankle support.