The only advantages the Big Five has over the MBTI, in my opinion, are: 1) it has the neuroticism dimension, which can have a pretty big influence on personality for someone who is very strongly limbic, and this should be taken into account when figuring out the T/F preference, and 2) it seems to be better at acknowledging that, on each dimension, some people's preferences (or whatever the Big Five term is) are going to be stronger than others. Even if, as [MENTION=18736]reckful[/MENTION] says, MBTI sources allow for the possibility of middleness/differing preference strengths, the type profiles are describing people who have four reasonably strong preferences, so anyone who has one or more preferences that are close to the middle isn't going to be described quite as well. Having said that, I don't know of any decent Big Five type descriptions, so it's only an advantage in that most sources seem to introduce the Big Five dimensions as scales where different people are going to be at different positions, and the MBTI preferences as black and white dichotomies.
I'm only interested in the Big Five because it lines up with the MBTI, and because of the Neuroticism dimension. I find the Big Five quite one-sided, not only because it tends to describe one end of each scale more positively than the other, but because it doesn't seem to really describe the more supposedly negative end of the scale in as much detail. There's a lot more to what, E.G. a P preference involves than "P's are not conscientious" or "P's are not J's".
And, "openness to experience" is an awful name for an N preference, although "intuition" isn't much better. I would think ESPs would be more "open to experience" than INJs; that term would lead me to expect that it was describing the kind of people who seek out lots of new sensory experiences in the external world.