aiiiiight, this is based on your initial upload...
first of all, the chorus and part of biggies verse over lap, which usually doesnt work, then it gets quiet and biggie raps his chorus... this sounds clunky and just doesnt work, instead try to loop the beat, have biggie rap his whole verse, then when he's done have the chorus from the mia song come in. then chop the biggie chorus out, you dont need 2 chorus' back to back. at the end let biggie finish the verse, which sounds like it will require some looping again. since you had to fade out biggie, sounds like his verse is longer.. so loop that shit, let the man finish. then do a chorus or outro depending and what you want to do.
also, if you haven't done so already, just the BPM of each song... this means the beats per minute.
To calculate your gonna need this: http://www.b-boys.com/classic/beatcounter.html
tap the button to the kick and the snare(basically the rhythm or pulse of the beat) you only have to do this for 15 seconds or so. lets say one song is 93 BPM and the other is 90. Then to correctly match the 2 you have to make the the same. So I don't know what your using, but in ableton theres a box in the corner with the BPM, you just type a number in there and it sets everything to that bpm whereas on turntables theres a little slider on each one that goes + or - 10 and you just do it on there.
Biggie is one of those MC's who the BPM's can be off and sometimes it still sounds on. Mos def is another, but that ussually not the case. So lets use the beastie boys as an example of how to beat match accapellas to beats....
Ussually in beat matching your matching 2 beats, typically the kicks and snares, in accapellas you obviously don't have any music so it makes it harder. So what I do is listen to where the lyricist is putting emphasis in his lines. so example, 3 mc's and 1 dj(caps lock indicated emphasis.)
THREE mC's and ONE dJ WE be gettin DOWN with NO deLAY mix MAster MIke what you GOT to SAY
Most the time in that sequence the emphsis is on kicks and snares. so when you have the accapella synced up correctly like this, it makes it sorta lock in together and works much better.
Not a bad first try though, keep on messing around. And remember, one you learn how to apply the rules, don't be afraid to experiment and deviate from them from time to time if it works.