Re the spur debate. If you know have excellent control of your lower leg and can apply the spur at exactly the right moment, they are an excellent tool. It is when you see riders kicking the spur in at every stride. I prefer a dressage whip, particularly for not so experienced riders. I attended a Steffen Peters masterclass on Saturday morning, he was the top dressage rider in the world in 2009 and watching him ride, he is brilliant, so soft, so controlled and just overall beautiful. He uses spurs, shock horror! His philosophy is that you should NEVER kick the horse, if you are trying to create sensitivity and responsiveness in a horse, kicking is merely going to make them dead sided. If you do not get a reaction from a squeeze of the calf, then move to give a flick of the whip or a touch of the spur. As soon as you get the reaction, remove the pressure and sit quietly.
Spurs DO have their place, of course it's great if your horse will be sensitive off the leg from the get go, but many people don't have the luxury of training a horse from the ground up and have to deal with problems installed from previous riders, thus other methods must be employed.
It should have nothing to do with leg strength, by all means lay a kick into your horse that could break it's ribs and be proud of having that sort of strength, but it is the tactful riders that succeed and pull out genuinely beautiful performances, not the ones that lift their legs sideways and get a great big kick up.