Moved the thread so you'd get more help but here is what I can offer...
Those images you like have outside light sources, the definition you want is caused by light and in your image you don't have much and not in the direction you want it to go.
I have a video on how to shoot bar & night club photography with a small light that is handheld and you can watch it on my blog at
Photography 2.0 just scroll down it's after my home made ring light how-to.
Your lens isn't going to change the output so much as good light and good light trumps fast glass any day. Basically in the first image you like there are two light sources and they look to be strobes fired to get the effect. One is high and 45 degrees on camera left and you can tell by looking at the shadows on the first girl because her shirt has the a downward shadow pattern. The second strobe is on the far camera right and you can tell because of the shadow behind the girls of the wooden beams cast on the wall. There is also some PP'ing and you can tell because of the trailer outside the window is too flat and the room is a little on the hdr side.
Image number two also has two light sources. One is outside the vehicle coming through the rear window and you can physically see the flare from it so it's obvious. The second light isn't so obvious but if you follow the shadows there is a fill light coming in from camera left so she isn't too dark. These could be continuous lights because of the high ISO look that was achieved, but it could be PP'ing.
My recommendations... learn to light better and everything will get better. You don't have to buy anything just learn to use natural lights, like lighting in the house, window light, reflections from water, etc.