The camera bag protects your investment in your photographic equipment. To provide the best protection of your equipment, use a metal case. When packing your case for a days shoot, never pack it to heavy, hauling around all that weight could cause damage to your back. Each piece packed carefully helps you to know where everything is. Carry smaller items in pouches and pockets attached to your person. Ideally, a case on rollers and that is waterproofed would be great.
When traveling by air you would want to consider buying a lead – lined travelers bag as it provides some protection for film against x-rays, though not 100%. An insulated film bag is used for carrying film but can also be used to store cameras in hot weather.
A correctly packed case can hold everything you need such as; different camera bodies, several lenses, at least on lighting meter, various filters. Do not forget cleaning products, lens hoods for when you change out lenses. Pack extra batteries, the last thing you want is for your battery to die in the middle of a shoot and not have an extra one. In order to separate equipment your case should be fitted with partitions held in place by Velcro or solid foam fitted to each item.
When working in crowded situations, a backpack type bag would probably be the way to go. Carrying your equipment with weight evenly distributed on your back leaves your hands free. Moving through crowds while taking pictures becomes easier.
Soft camera bags allow easy access and when packed properly, can protect your equipment well. When carried over the shoulder it also leaves the hands free to take pictures. In order to protect your lens in a soft bag use hard leather tubes to store them in.
Camera bags like your cameras are a personal choice, yet essential to the trade.