Need suggestion of buying a DSLR?

I'm thinking to buy a DSLR, well i'm still a beginner, so i need suggestion from you all… Buying Nikon D3100 or Canon 550D or any other better choices?

I use the camera mainly for outing event, party, scenery shot,
I will prefer the one who can take good quality under low light condition like karaoke room

There's another question, do i need to buy another lenses or just use the lens included along with the DSLR?

It depends on your budget really. Like for like, there's no real difference between Nikon and Canon - someone will prefer one, whilst others will prefer the other. Personally I'm a Nikon guy, but I know people who've switched "to the dark side" and have stated there isn't much different. I shoot a D40, whihc a few years ago was the base model DSLR from Nikon - I think this is now the D3100.

Any DSLR will do the things your looking at doing much better than any compact. Regarding how a shot comes out in low light depends on the lens. The kit lenses will be fine, but if you want to start getting really in depth with your shots - I mean editing every little detail in photoshop then you'll probably need a better lens.

Always remember, it's better to team up a high end lens with a low end body than a high end body with a cheapo lens.

If you're looking at low light photography of karaoke, you may find it impossible to get a decent shot, without a tripod and a long exposure. How a Google around and figure out the relationship between aperture and shutter speed - and remember, it's all a question of practice.

For a start the kit lenses of these cameras will do just fine, but be aware that they are not particularly low-light capable. For this you'll need dedicated lenses, usually prime lenses with a wide maximum aperture. So on the long run expect to pay another about 1-2 times the cost of the camera body on additional accessories such as more lenses, tripod, flash, bag, filters.

Both are fine cameras. The D3100 has better video recording capabilities and does a little bit better in low light, but the 550D offers a more comprehensive overall feature set.

The D3100 has one big handicap that you might find particularly severe - there's no cheap 50mm/1.8 lens for it that will autofocus on this camera, unlike the 550D.
For the D3100 you'd have to get the $350 50mm/1.4G (not D!) instead of the $140 50mm/1.8D. Then again, the D3100 is cheaper than the 550D, so you could direct the saved money towards that 50mm/1.4 lens, which is even better than the 50mm/1.8, and you might come out at the approximately same total price. Actually, i think i'd do that, as this would make an awesome combination for low light, and it's good to invest more into lenses than into the camera body - the lenses will serve you for decades to come, the body will be replaced in a few years.

These 50mm lenses are very good in low light and especially suitable for portraits (be aware that they don't zoom at all though). For other low light use, such as parties, i'd recommend a 35mm/1.8 or whatever the Canon counterpart is.