Which is the better one?

I wud like to buy a dg cam probably nikon p510 or p520 or canon sx50?
which is th e better one?

Without knowing how you plan to use the camera i can't give the best recommendation. Those are both big zoom cameras, if you don't need to take a picture of a bird from 250 feet away you could have a lot better options.

Personally i don't recommend either in general. I think smartphones are plenty good for pictures on the go, and when i want to do family portraits or what not i use my DSLR for absolute quality.

You'll get a Fujifilm that does the same job for half the price of the Nikon.

Unlike the L-series (total dross) Nikon's P-series are actually quite nice cameras, but far too expensive for what they are - bridge cameras. The SX50 falls into the same trap.

Fujifilm are just as good, just as experienced and far easier on the pocket - they own the bridge camera sector of the market for a reason. Of course, if you carry a Fujifilm, people might think that you can think for yourself, rather than listening to the braying of two companies whose reputation is based on professional kit that costs an arm, a leg and your first-born son.