Ati radeon hd 4850 1gb or ati radoen hd 5570?

The HD5770 is ~20% better and offers DirectX 11 while having a lower power consumption, outputting less heat, and is, in general, a better card.

what about the 5570?

Vastly inferior to either card. The HD5750 = the HD4850 in performance.

If you need a low profile card then go with HD5570, but if the normal card will fit into your case and you have enough power from PSU then get that HD5770...  

The HD5570 is DX11 but the HD4850 is nearly twice as powerful. They aren't comparable.

you are using Hd 4850. what about the temperature and heat with this card. is it difficult to control heat and temp from this card
please do replay.

Digvijay

5570 does look puny in front of 4850. It may be a next gen card, but pure performance wise, no way a 5570 could touch a 4850. Of course, things would be different if temperatures, power consumption and noise were your priority. Otherwise 4850 hands down.
P.S.: If you are planning on a 4850, also consider getting a 5770 instead (or a 5750 if a queiter and cooler card is needed).