What is the difference between a Specialist and a Corporal in the Army? Inquiring Marine minds want to know.

One reason why the rank exists comes to mind: in the 1990s, and likely as will happy again with force drawdowns, etc., points for E-5 jumped for many MOSs to high levels, unattainable by many E4(P)s, but command still needed junior NCOs inhabiting roles like "team leader." Hence the ability to draw upon senior or promotable E4s to fill those roles. In times when you can throw a stone and hit a sergeant, it doesn't seem relevant, but it gives commanders a pool of junior leaders with true authority when times get tough. SPC commanding other SPCs in a fire team is problematic - having that command-appointed corporal gives everyone a rank-based cue on what's what.

CPL is an NCO while a SPC is not. They are both in the E-4 pay grade so movement between the two is called a lateral appointment. The CPL rank is normally used in situations were there are a lack of NCOs and a SPC (serving in a NCO billet) had demonstrated the ability lead and accomplish the mission.

Specialist is an automatic promotion. A Corporal is a command recognition of someone's abilities while they are serving in a leadership position.

Specialists are the equivalent of Lance Corporals. They just get paid more.

A Specialist, E-4 is a junior NCO who is in charge of a specific task. Like being a cook, a clerk, med/legal/admin tech, chaplain's asst and etc.
A corporal E-4 is a person who is charge of people, squad and etc. An infantry/armor/artillery position.

There were Corporals in the Army way back in the days. If I can remember well they were only in Infantry and always were squad leaders. Specialists usually have a tech job the civilian equivalent of a techie.

Arent they spelled differently???

1stSgt (Join to see) , I think your question should more be "What is the difference between an Army Corporal (CPL) and a USMC Corporal?" I think the answer to that question would shed more light to how the Army CPL is used. Now, you have probably reviewed a lot of the answers on here and noticed they vary, but generally have the same endpoint. The Army CPL is an NCO who is serving in a SGT or above billet, in their Primary MOS.
You probably heard the commonly mis-quoted piece that the CPL should be promotable to the next rank. While some leaders think they should, they are not required to be promotable (I think that is an Army CSM thing). Because I understand the USMC Corporal's duties and scope, I have used CPL in the Army to develop that young hard-charging Soldier who COULD work as a SGT, but is not where I think they should be before wearing SGT stripes.
I hope you continue to enjoy the responses...... :)

a CPL is in a position of greater responsibility. He is closer to being an NCO than a SPC (due to showing leadership traits)
same pay grade but one has shown more leadership potential than the other
Example: an Abrams tank has 4 positions: TC, Gunner,Loader and Driver. The Driver can be an SPC but the gunner can be a high speed CPL. Both are E4s on paper but one has much more responsibility than the other.

One is a NCO and one is not.