Solid axle suspension vs Independent Front Suspension

     Solid axle suspension:

   Solid front axle refers to the presence of a solid axle beam that connects the front wheels laterally. An SUV with solid axle and 4 wheel drive is also called as a live axle.
     A live axle consists of a central differential in a single housing that also contains driveshafts that connect the differential to the driven wheels.
   The differential is connected to the engine via a swinging driveshaft and a universal joint. The complete assembly may typically be suspended with leaf springs or coil springs. 

  A diagram of front solid axle without a differential

                                        

A solid front axle suspension with front differential on a JEEP Wrangler.

The complete assembly are suspended by coil springs here

 Notice the front differential, solid axle beam and the steering rack pinion

            The front differential and solid axle suspension

solid axle suspension behavior on uneven terrain

Notice that the differential is also lifted slightly due to its inclined angle

The scope for articulation in an SUV with Solid axle suspension

  Independent front suspension:

             Independent front suspension is a suspension system that allows each wheel on the front axle to move vertically independent of each other. This is contrasted with a solid axle in which the wheels are linked thus affecting the wheel on the other side. Note that 'independent' refers to motion or path of movement of the wheels/suspension.

         This system offers a more comfortable ride when compared to a solid axle suspension setup as terrain undulations encountered by the wheels are absorbed by that wheel's shock absorbers and is not transferred to the entire axle including the other wheel on the same axle.

           
       It is common for the left and right sides of the suspension to be connected with anti-roll bars or other such mechanisms. The anti-roll bar ties the left and right suspension spring sets together but does not tie their motion together.

 The wheel joint in the front axle

  Notice that though the front wheels are not aligned in respect to their positions, 

the body remains composed and does not tilt.

This is because the undulation is absorbed by the independent suspensions themselves.

Notice the presence IFS (Independent Front Suspension) in the Mahindra Thar CRDe 

IFS

 A 4X4 with IFS

Notice the differential behind the IFS on the Mahindra Thar

Notice the limited axle articulation on an SUV with IFS

Conclusion:

Solid front axle suspension:

 Pros:

• Virtually bulletproof and can take any kind of stress and terrain.
• High articulation
• Simple mechanisms and durability
• Chances of damage during offroading is lesser when compared to IFS

  Cons:

• Bumpy ride and not as comfortable as with IFS.
• High speeds on rough roads with ground undulations can literally throw the passengers around in the vehicle
• Vehicle is very unstable at high speeds

Independent Front Suspension:

Pros:

• Comfortable ride
• Stable at high speeds
• Vehicle stays almost horizontal to the ground while articulating

Cons:

• Limited articulation
• Delicate when compared to solid axle suspension during offroading as obstacle like rocks, tree roots, ruts can seriously damage the IFS.
• Reduced ground clearance while articulating because the entire axle does not move.