Well I prefer shorter anime series, because you can finish them faster, some of them has awesome stories which gets you into so much you can finish it in one day.
But I don't turn down longer animes. I usually pick them up and watch them whenever I have time it takes forever to finish some of them, I tend to drop those halfway and then get back to them after sometime from the place I've stopped. It always depends on the plot, story, good desrciption for me. Since spring I've been watching Naruto Shippuden with my friend, I have stopped for a bit with it now. Since my friend is away and won't push me to watch it x'D and also I have a lot of stuff going on in school, too busy for anime in other words. So it's in a little wait list until I have more time.