Actually, you should learn both BJJ and MT as they complement
each other - one for stand-ups and one for ground fighting.
BJJ is more practical then traiditional Japanese Jiujitsu in the
sense it doesn't necessary have gi's, which the Japanese
practitioners rely so much on (and consequently feel lost on the
streets where their opponents don't wear gi's). However, BJJ is
known to have its limitations too - eg. too complicated/confusing
for many (like myself, with a simple mind). Its also known to have
its limitations on the streets due to rough grounds (your back and
knees will get scraped like hell).
I heard that Wing Chun is also quite practical and simple to
comprehend. I've heard of Wing Chun guys trapping the tricky hands
of boxers (which means they probably can trap the hands of a
streetfighter too, which have relatively-simpler movements).
Having said that, I only had one day training in Wing Chun
. Some experienced
Wing Chun guy was trying to teach me sticky hands (their form of
sparring). Was not very impressed leh....I managed to slap him a
few times in the process. 
Honestly, for street situations, the best is still a combination of
western boxing and simple wrestling lah. Oh, and soccer too...for
kicking the opponent's shins.