Why am I responding to a 6 year old thread??

Maybe op can give us an update!
The initial question itself doesn't have to be regarded as ridiculous, although I think when embarking on such a journey as a Rach concerto, one should probably have very strong and personal feelings... The op, now years ago, said he or she has studied nearly all of the Rach preludes/etudes... if this is true, then op could approach any of the five concerti (counting Paganini as #5) because the complete Rach preludes and etudes easily cover the range of challenges you'll discover in the concerti.
Personally, I've played 2 and 3, and only 2 with orchestra. They are not easy pieces! Rach 3 deserves its reputation. That said, nothing is unplayable. It's all very pianistic (It's Rachmaninov

after all), it's just very very demanding. One should expect a solid year of learning all the notes/letting them sink in. By the time you are ready to perform a Rach concerto, you'd better feel every single note in your bones, like you were born that way.
Now, the pecking order... I'd say Rach 3 is the most difficult in practically every regard, musically and technically. It really is. If I HAD to order them in terms of technical difficulty (a stupid concept to begin with) I would probably go:
1. Rach 3
2. Rach 4
3. Rach 2
4. Rach/Pag
5. Rach 1
I'm not totally sure about my placement of Rach 4... And don't let this make it seem like Rach 1 is easy! Keep in mind they're basically all among the most difficult works written for piano, so... anyone approaching these pieces at all should already know fully what they're doing.
Op, did you ever end up studying one of the concerti? I recommend to anyone and everyone, no matter the level, to familiarize yourself with these concerti through listening to the great recordings and absorbing/thinking about the music. Taking it upon yourself to study the notes from the ground up is probably not the right approach for someone who isn't already very familiar with the music.
I would even go as far as to say that anyone out there who plays a concerto like Rach 3 very well was already extremely familiar with the music before they touched a single note. By the time a pianist chooses to approach a piece like Rach 3, or the Liszt B minor, or the Hammerklavier, or the Goldberg... it's probably been rattling around in the head for years already.
Just some stuff to think about. In the end, I encourage doing whatever you are truly inspired to do, even if it breaks some of the "rules." Go with your gut!
