What were the major differences between northern presidential and congressional plans for reconstruction and which was more important.
To answer the last part of your question, I think it must be said that Congressional, or Radical Reconstruction, was most important. First, it was the plan that went into effect and was how the southern states were readmitted into the Union. Second, it must be considered most important because the Radical Republican plan contained the passage of the 13th, 14th, and 15th Amendments to the Constitution. The 13th Amendment abolished slavery in the U.S. The 14th Amendment did many things. It said that anyone born in the U.S. is a citizen of the U.S. This made all former slaves citizens. Next it said that no state could deprive any person of life, liberty or property due process of law. It also said that no state shall deprive any person the equal protection of the law. The 15th Amendment stated that no person could be denied the right to vote on account of race. This allowed African Americans the right to vote. The passage of these three amendments makes the Congressional Plan for reconstruction the most important.
The major difference between the presidential and Congresional Reconstruction plans is that the Congressional Reconstruction plan (aka Radical Reconstruction) was much more harsh towards the South.
Lincoln, and to some extent Johnson, was lenient to the South. He wanted the South to be brought back into the Union as soon as possible. The South was to be allowed to govern itself. However, when the South started to do this under Johnson, it quickly started to take actions to oppress the freed slaves and to do other things that annoyed the Radical Republicans.
Because of this, the Congress imposed military rule. This took self-government away from the former Confederate states and replaced it with a military occupation. I guess I would say this was more important because it lasted longer than presidential reconstruction did.