for me what decides it, is what the day will probably bring and be like. so, usually all i carry is a do-it-all-folder or multitool and a surefire torch, plus my keys with mini-knife and mini-light on it.
now, when i go camping or fishing or something like that, i like to add a fixed blade to the gear. simply matching the EDC to the occasion at hand.
legality is ofcourse also an important issue. even though during a preventive search on the streets everything from a small SAK to a pair of scissors will be confisquated anyway (they do it because they have the authority and "people shouldn't be carrying knives", they know nothing about what's legal or not, they take it all and you can forget about getting it back, even though it legal.......

), i do make sure that all my stuff is legal to carry though, carrying an illegal knife in an anti-knife country is about the dumbest thing you can do.
sheeple-friendliness is not really an issue for me, i don't care what they think. although there is this one thing: i don't like sheeple spotting me using my knife and calling the police because they have "spotted someone with a knife!". i don't let it force me to carry small blades though, i just carry black coated blades instead and/or keep a low profile if chances of "knifer-sightings" are increased.
especially over here in The Netherlands it's at the very least odd and suspicious to the police if someone wears anything that resembles a knife at all. even carrying a SAK over here means that "you must be up to no good". Holland is really anti-knife, i can tell you that.
a little off-topic, but, it really pisses me off me when nice people are being pulled over for general vehicle inspection, tested for DUI on tuesday afternoon, given a ticket for a bicycle-light that happens to ran out of batteries, getting a speeding-ticket for driving 2 mph too fast, and all kinds of stuff like that. and while you're standing there you just KNOW that at that very same time, somewhere else people are being murdered, shops are being robbed, women are being raped and children and animals are being beaten. it makes me so mad! :grumpy:
rant off.