A bunch of keys is better - fully normal to be carried, have an assortment of keys, grip one Yale style between fingers and you have a pokey thing with a jagged edge that’s ideal to scratch with a level of stabbyness to cause pain to an attacker, ideally encouraging them to back off enough for you to run
I know this isn't the point of the thread but as we're here...the 'bunch of keys' thing is another 'self-defence' myth that has been passed down through the years with little basis in fact/practical use and will do most people more harm than good.
If you're taken by surprise, you simply won't have time to take them out of your bag/pocket, arrange them between your fingers etc.
Even if you have them perfectly placed and held in your hand, they're of very little use. The weapons you're trying to emulate (things like the Indian bagh nakh) have rings attached to the grip for your fingers to go though, to stop the small blades/spikes moving/sliding in your hand. A key/keys will move/slide all over the place on contact with anything, or be pushed back into the palm of your hand.
Your attacker will be full of adrenaline; even in the event that you were extremely lucky and were able to pierce the skin on their body, it's unlikely they'd feel it immediately. For context I have been stabbed in the leg with a small knife causing an inch deep, two-inch long wound, and didn't realise until about five minutes later when someone else pointed it out to me!
Essentially your only option for using keys to cause serious damage to someone approaching you from a distance, is to punch them directly in the eye, which realistically is unlikely to happen.
If you are in a close-up situation where an attacker already has a hold of you/is on top of you/pressing you into a wall etc, you have a much better chance of effectively damaging them by - and forgive me because this isn't pleasant - biting their ears/nose/lips or gouging their eyes with your fingers/thumbs.