Are there any cons of flying in mode-4.
i have developed a habit of flying my planes in mode-4, whether it be a simulator or field flying. Few days ago i realized that its rarely used.
So, is there any drawback flying with mode-4?
What makes mode-2 so popular?

What I personally feel the advantage of learning in mode 2 is

1. Many learn flying on a planes without rudder or not using it at all, so the left controls are used only for throttle and the right side controls for elevator and aileron.
This eliminates the movement of the left side controls in all four directions and makes it easy..

2. And also controlling the ailerons in mode 4 or mode 1 may disturb the throttle stick while learning to fly.

I use mode 2 because being a right-hander it is easy to control the pitch stick and roll stick with the right hand, both of which demand more precision than throttle or yaw. So i feel yaw and throttle on the left is a good idea.

General discussion on advantages versus disadvantages, mostly between modes 1 and 2.

http://www.rcindia.org/rc-general-topics/mode-1-or-mode-2-pinch-or-thumb/

http://www.rcindia.org/rc-general-topics/converting-from-mode-1-to-mode-2/

If you are an outlier (like mode 4) the main problems are :

1.  You not being able to fly other's aircraft, or others not being able to fly yours (for purposes like test/trimming flights)... without reprogramming in one of the common modes.

2.  Lower ability to buy/sell stuff in the second hand market... not a big deal as long as you are ready to change modes inside the radio (most of them require you to physically open the radio up).

I fly in both modes(2,4), but mode-4 seems much comfortable to me.So i have developed the habbit i guess..

No, generally there is no requirement of changing up the radio hardware.. all we need to do is to just swap the "rudder" and "aileron" channel while attaching servo wires.
Above method might not work with flaperon function though..

Right, it is easy to switch modes on the radio between modes 2 and 4, not so between some other combinations especially between 1 and 2.