Not sure exactly what you are talking about by "general snap switches" versus "standard disconnect switch". But based on how you worded your question, my answer is both are required.

The circuit breaker in the panel is not intended to be an equipment shut-off point. Plus there is the safety issue. The electrical panel normally located in a closet away from the equipment it serves. Without going through a lock out/tag out procedure, there is the possibility that while someone is working on a fan, another person could enter the electric closet and flip the breaker back on harming the technician working on the fan. Additionally, the breaker switch could be providing power to other equipment.

Having a switch adjacent to the fan allows just the fan being maintained to be turned off, plus the need for lock out/tag out is eliminated because the technician is watching the switch. For the size fans you are talking about, the disconnect will most likely look like a "light switch". However it will be more robust. One thing about the local disconnects is that they don't provide over-current protection.