Really depends what you want to do in the future, I guess. Deeply clichéd but you usually need good work experience in order to get a graduate job, for which a 2.i would suffice. If you want to do a funded PhD in the humanities, these days you almost certainly need a first. But, all my friends with 2.1s and even a couple with 2.2s have gone on to get well-paid graduate jobs, mostly cos of their work experience and really good performance at interview.
As for the disadvantages, from personal experience, you can end up super focused on academics and ignore everything else. I definitely did that and to be perfectly honest would utterly useless at Project management, marketing and HR managing which my friends who graduated with humanities degrees now do. I am dead proud of them for what they do, we just have different skillsets I guess.