I own a 2254, and a planet ocean with the 8500.
The 2254, and new SMP are very different watches. The fit, finish, and action of things like the bezel, crown, bracelet, clasp, etc are much more premium on the newer Omegas....You also can not feel any rotor wobble on the newer movements whereas I definitely feel it from time to time on my 2254.
Having mentioned all those things, I love my 2254, and will never get rid of it....I love the sword hands, subtle wave dial, lume, and classic/timeless styling. I think it has, and will continue to age very well. It is also very thin, light, and comfortable with a tapering speedy bracelet.
It all depends on what you are looking for as to me they are both automatic Seamasters with the same water resistance, but are pretty different otherwise.