Excellent advice on this thread but I must adda vote of confidence to extending leads.
Hated by many 'I know best about everything to do with dogs' type people the world over.
well, I have an Akita, he's 6 years old, since adulthood he is let off the lead next to never. He is not aggressive but he is dominant and if anything tries to usurp him, he will show them that they can't. It's not worth the risk.
I have used the flexi Maxi and Giant leads all his life. For me, they offer the perfect solution. I have full control of my dog because he responds to commands. If another dog looks like it is going to be trouble, I can very easily shorten the lead, lock it and be close enough if the other dog should be so stupid as to try and have a go. I have been in quite a few of these situations I can tell you, some dogs and some owners are just plain stupid.
I would not recommend extandable leads to people who are not going to use them properly or go through any proper leash training first but that should be common sense. I switched to extendables after training on a proper lead. This is important I think. I would say the communication you give through the extended lead is lessened as it always has some tension to it so Aural commands are important whilst using the lead, much as they are when a dog is off leash. I can give a flick on the extendable lead without locking it and my dog will come to my side, just the same as you would with a fixed leash. If you use something consistently with a dog, it will be trained to use it properly, that is how training works. Why should extendable leads be any different.
My wife has a friend at work who has a very young st Bernard. He was literally crying one day and threatening to get rid of the dog as he could not enjoy walks with him as he kept running off causing mayhem and almost getting himself killed, he was an absolute terror for pulling on the leash. we advised him to get a halti collar to reduce the pulling on the leash and an extendable lead for use on long walks instead of letting him off. He actually ended up combining the 2 at the same time and now enjoys long walks with his young dog who has responded to the new equipment immediately.
The moral of the tale... don't knock it 'til you try it and don't believe all you read about the 'demons' that are extendable leads.
Make sure you buy a good brand, don't let any freying areas on the ribbon turn into tears as you don't want your lead to snap. and I recommend spraying a little WD40 into the spring mechanism to protect it from water whilst out and about.