That's an interesting point you bring up, superstition, about Rachmaninoff's sonatas. I personally prefer the D minor because it's more expansive and epic, and because it takes the three-movement sonata form to twice the length that one would normally be accustomed to hearing yet is still successful. The 40-minute sonata that works is a rarity - the Hammerklavier and a couple of Schubert's are the only ones I can think of other than Rach 1 (not to mention that the latter is three movements while the others are four, which makes it more remarkable - the next longest three-movement sonata to Rach 1 that works is what, the Appassionata at 25 minutes?). Played poignantly and not stagnantly, Rach 1 can really work, even (especially) in the 17-minute Allegro molto. When I hear Rach 2, moreover, I hear a piece that's very often trying to be its older brother, written in a language that sometimes misses the romanticism and expansiveness of 1907 and leans more towards the sporadic style of late Rachmaninoff. Particularly in the cut version, it sounds written for a shorter attention span.
The comparison between Chopin's and Rachmaninoff's sonatas is tricky. Chopin 2 was written in what I consider his prime, when he wrote pieces such as Ballade 2 that were focused, to the point, and never wandered. In later opuses, I daresay it sounds like Chopin stopped planning his pieces as much. Ballade 3 sounds like he stopped working after the first 2 1/2 pages and picked it up again a while later. Scherzo 4, the least pleasant mature Chopin piece to listen to for me, sounds as though he came up with a theme and tried to distribute it across 12 minutes instead of planning more in depth. Even Ballade 4 meanders a bit in the middle before finally getting down to it in the last few pages. And the first movement of Sonata 3 could have been cut - it wanders too much in my opinion. I don't know what it was, but something about Chopin's late style causes his longer pieces to be less interesting to listen to for me, perhaps more cerebral and intellectual but less captivating, almost like Rachmaninoff becoming Medtner.