About the discussion whether to use a mouse or a tablet, which one would you recommend to someone who hasn't tried either yet ? (considering money is not a limiting factor)
Hrmm, well I think that depends on which you would personally feel more comfortable putting the effort into learning. Though, if overall speed factors into it, I think a tablet's built in pressure sensitivity function adds a lot down the road towards finishing things faster (because you don't have to worry about changing brush sizes to colour smaller areas, just press softer), but at the beginning when still getting the hang of things you aren't going to have the control yet to colour everything with a huge brush.
I really wish there was a way to try out a tablet before purchasing it, but I've never seen that kind of option anywhere. The stores around here never have a demo model set up or anything. :/ It's very hard to call one 'better' than the other, as both mouse and tablet just require dedication and an understanding of how they function and what limitations they pose that you need to learn to work around.
Chances are you already own a mouse, so you can give it a whirl and see how you feel about it. If you have an electronics store near you that has some sort of 'x many days to try it out' return policy, then maybe try snagging up a tablet for a few days and seeing what you think. Some people feel silly returning things after they've used them, but that might be the only option to try one out and if the store states a policy that you have so many days to return it even if you've used it, then that's a thing you can take advantage of to see what you think.
They are both going to feel odd though, but maybe it will give you a better idea of what you're getting into.