If you asks what pianoconcert, Rachmaninoff 2 or Schumann A minor is the easist....my God, I think both of them are too difficult for you if you asks this kind of question. -Choose pieces that fits your level! I suggest some of Mozarts pianoconserts ..or Beethoven, Nr 2 or 3 is popular.
Chopin Concerto No. 2, it's so great, if you want a Romantic composer. You don't want to do Beethoven? I envy you that you'd think of trying Schumann, a concerto of all. Slow or fast, I somehow always ran out of my fingers with Schumann. I felt like learning Chopin Concerto No. 2 is easier than even Kinderszenen, I am sure I will be killed by all of you by saying this. (And I did indeed try to learn both of them, so I am not joking)
Well, Chopin Concerto No. 2 is shorter, and also it's supposed to be easier to actually work with Orchestra (Of course, I'd never have such a chance). I never tried Chopin Concerto No. 1. My teacher suggested definitely No. 2 for my level, so I trust No. 2 is easier than No. 1. He also said I may peak at Rach concerto No. 1. He said it's a lot easier than Rach No. 2. Schumann? Not on the table for me.
I trying 1 now and Itīs so easy I just play It of sheet without some technique problems of course in slow temp.
Stevensk, no no no, I will never have any chance to play with an Orchestra. I am simply a amateur dreaded adult hobbyist who likes to delve into every possible piece in the world! But because of that, I can definitely suggest if there's anything even someone like me can try, then, all the wonderful piano students will definitely be able to handle.