Akshay,
I haven't used the Bushnell beyond the shop. The 50 in the 7x50 specifies the objective or light gathering ability. So the 7x50 is better in lowlight than the 8x42. The 8x makes the field of view narrow. 10x makes it difficult to locate the bird or animal and magnifies the shake. The 7x or 8x versions are fine.

However, be warned that in Binoculars, these models are the kind of entry levels. So don't compare it with someone else's Leica or Swarovski models. There is always a difference in the glass used.

Cheers,
Sabyasachi
PS: Shifting this to the equipment discussions section