@Hari Sud,
@mans.randhawa ,
@Lone Ranger.
@arnabmit has already presented a general explanation of the differences between the ALH and the LCH. I'll just add a few points of mine to his explanation.
1. Side by side seating v/s Tandem Seating arrangement:
The general understanding is that tandem seating is better for attack aviation while side-by-side eating is preferred for transport aviation. The theory is that in tandem seating, the pilot sits in back with the weapons operator in front, enabling better view to the WSO to aim weapons, while the pilot being placed higher, gets a better view for navigation.
This results in unhindered 180 degree (minimum) view for both the pilot and the WSO, with the WSO getting a better view of the ground.
This logic was first employed on the AH-1 Cobra which too featured a cockpit redesign as compared to the UH-1 Huey on which it was based.
And apart from that, you also have a slimmer front face profile, always an advantage when facing AA guns or unguided munitions.
2. Structural redesign: For the LCH design, you are basically shaving off the entire structure that was used to hold the passengers in the ALH. In short, that means you are saving considerable weight. Now
that weight saved can be used to provide increased protection (think protection against 14.5 mm AA), increased structural rigidity and even increased payload. All of them are very very important, and would take me atleast a post each to do justice to their import.
Also, the fact that the design is now slimmer, with loads concentrated near the longitudinal axis allows for superior maneuverability, especially when loaded.