Ask HN: How do you split the equity pie?

I've always found very hard and confusing the initial splitting of equity when starting on something with co-founders.

Here is my current situation: I am a software developer and currently planning to create a web-based product. To do that, I am planning on going into business with a designer and a person who will be responsible of making presentations to potential customers and marketing.

How do I split the company in this case? Do we go 33% each? Or do I try and negotiate a lower percentage since I am starting the whole thing?

I am currently leaning towards splitting the company in 3 since it is an equal risk for everyone and an equal amount of work (sort-of of course). Furthermore, I think by splitting the company in three, we will have a better relationship and better motivation to make this work.

Please share your thoughts and experience on this.