Pros
Multiple opportunities. Pressure at a lower levels while working for a particular customer is bearable. Risk of job loss is very low unless you shoot one's own leg.
Cons
HR not very helpful. Moving up the chain, you hardly can get any assistance or opportunities. Growth is highly dependent on customer(that management is very sensitive to) you are supporting. Resignation is the only way to increase a salary or band. Huge variation in salary levels for a role. Tenured Graduate trainees end up earning more than more experienced resources at same role. Unreasonable targets at higher levels with no support from peers above. Even though you may not be treated well at a higher level but there is a huge dependency. As the customer relationship ages, relative importance reduces. Worst hiring. Resources can increase their salary by 300/500% by moving out & getting rehired after 2 years.