How Does One Make A Choice ?

Well, it's official, pretty much, since I've made my decision. So I might as well tell about it on here.
Clients of our department (another department) have shown interest in 'hiring' me. In short, I've been offered a different (better) position. And as I was offered this, it made me realise how much fonder of my job - or rather, my department - I am than I thought I was. So there's the explanation of my workaholism: I'm part of a great team that grew to rather big proportions since I joined it.
The new department has two very great appeals.
One, it's much more in lines of what I want to do. Basically, a branding team is forged and they want me on board as website manager / designer / technical jack-of-all-trades. Basically, I'm pretty much exactly what they're looking for, and a little beneficially more. It'll be publishing, writing, designing, ... it'll be utilizing what I can do AND what I like to do, a lot more than my current job.
Two, it's a brand new team who are going to set out and try a lot of things they've never done before. In other words, a similar department as my current one was when I joined. Back when things were still fun, we were inventing ways to make things work as we went along, we went around the books, we got things done.

But my current department has become like a group of close friends to me. And when I joined my current department, three other guys went from where I worked along with me. This step I'll be taking alone, and I know practically no one there. It will also mean I'm taking on a lot of work in the upcoming half year, and I already have some 10 weeks of vacation time built up that I'd really really like to take up. So that'll be very difficult to figure out. If I stayed, I'd have a stable, predictable work situation, I'd be able to take up my vacation time... and last and certainly not least, the relative stability makes it possible for me to work on my comics and Probeersel.com on the side. Which is why I went to work for my company to begin with.

So for weeks now I've been walking around with this. How does one make these choices ? Everyone told me I should follow what my heart told me but my heart told me jack shit.
So today I flipped a coin. Heads, I leave, tails, I stay.
It was tails. And it felt wrong immediately. So that's how I made my choice.
Even more busy, workaholic, exciting times, here I come...