I would say for urban EDC and you can only have one, for sure go with the multi-tool. Much less threating to the masses at work and out in public, a cop is very unlikely to hassle you for it. Besides, in a urban setting your more likely going to have to tighten up engine components and open boxes then you are going to have to scale a fish or make a lean to ^_^.

Somebody mentioned the protective abilities of a knife as opposed to a multi-tool and thats true, a multi-tool doesn't offer much in that way. Personally I carry a colapsable steel baton and dog replent pepper spray. The baton is a heavy hitter but I think is better than a knife for conflict. A knife forces you to really injure a person with the distinct possibility of death, this "all the way" nature of a blade can make you hesitate or possibly get you in trouble afterward (would not be the first time someone was accused of over agressive defence, not to say those laws are flawed, just saying they do exist). A baton however can cause grevious damage but the possibility of death is greatly reduced (provided you don't strike to the head). Police often use their batons to strike the knee caps and shins of hostiles, this immoblizes (not to mention really hurts!) without the danger of killing a guy. Just my 2 cents.