Toshiba or Lenovo/Dell. Please suggest with whom and why should i purchase? I'm confused?

I will suggest you to go for Lenovo due to its strong hardware. Lenovo's hardware manufacturer by IBM. Its hardware strongest then any machine.

Mainstream Windows laptop mfg ratings:
Lenovo is the number one, followed by Asus, HP, Dell, and Samsung.
At the bottom of the pile are, from the bottom up, Sony, Acer/Gateway, and Toshiba.

Purchasing a laptop is a highly personal decision. You need to decide what type of keyboard you want: do you want a full sized keyboard or are you okay with something smaller? Do you like or despise the chicklet keyboards like apple uses? Do you want a backlit keyboard? Do you want a numeric keypad? Do you want a touchpad and/or point stick? Do you want 2 mouse buttons or 3? Do you want them above or below the touchpad? How large a screen: 13"? 14"? 15.6"? 17"? If you are highly mobile, then smaller is lighter. If you don't move around much then bigger means heavier but a much more visible screen. These are all things to ponder which have a significant impact on how happy you are with your laptop experience.