It's best to go to a few different clubs and see which best suits you. I'd be tempted to say that no one martial art really encompasses everything you could want/need in a real life self-defence situation, so your best bet would be to find a club that is open to other styles - or even just going for MMA. (Edit - your best bet is to not actually get in to a fight..!)
You should definitely make sure whatever it is you're learning is based on full-contact sparring as training on semi/no contact isn't really worth your time unless you're only looking to look pretty.
I've been doing Karate for the last 7 years, and I absolutely love it. I'm really lucky though, as the club I am part of often attend seminars and run group sessions with instructors from different Martial Arts including Judo, BJJ, Aikido, Kendo, Escrima and KAPAP.
I'd personally say KAPAP is the most 'gritty' realistic version of self-defence I've tried and so it'd probably best fit what you're looking for - but like I said, look around a few different clubs and you might find something really takes your fancy.
For me, I fell in love with Karate even though only half of what we do is full contact 'street wise' training - I just love the art in it and the physical training. So you might find you end up enjoying something like Tae Kwon Do that is stereotypically more 'showy' than practical.