[Uncle Bob]

Well it would definately protect better but it comes down to what use you subject it to. If you're riding in 100 degree heat a mesh jacket will give you slightly less protection than a good leather jacket but it may help you avoid heat stroke which would increase your chances of an accident.

Would rather see you with the mesh jacket than not wearing the leather because it's too hot. Of course over time you will probably collect a few jackets and choose the one that gives you the most protection according to the weather.

Sorry but there is not one do it all jacket out there yet. Heavy leather will give maximum abrasion resistance for sliding down the road but many good leather jackets depend solely on the leather for protection and don't have built in armour ( the Alpine star jacket does not come with back protector but it can be added ). Textile jackets usually have more armour, elbows, shoulders and back but are not as abrasion resistant. Textiles also come in different configurations to be either more windproof/waterproof than leather or in more breathable fabrics such as mesh.

Joe Rocket just came out with a jacket that has zip off panels that'll allow you to use it when it's colder and/or raining and then zip off the outer shell to uncover the mesh panels beneath making it the closest thing to a year round jacket available.

If maximum protection is your goal then a good leather jacket with some type of ventilation panels built or perforated leather is your best bet however if comfort is also a priority then textiles should be given serious consideration depending on the conditiond you ride in.

BTW no matter how good the jacket, usually you need to buy the matching pants for max protection, the jackets usually come with a zipper in the back that zips onto a matching zipper on the pants. Should you be sliding down the road feet first this will keep the jacket from riding up your torso and exposing skin.