I have to admit I really like the Omega blue better. It has a richer blue color. I also like the red tip the third hand as well. The Rolex is too bright for my taste. It's still a killer watch however.
So just my personal thoughts, BUT the Sub is too bright in all blue. The Omega is darker and more appealing to me, but I dislike the wavy dial. So for me, they are both great watches, but the wrong configuration and color combo for me. Just my own .02 worth. You asked...
The blue Omega. I am not a big fan of the cycloptic date window. There is a black Submariner without date, and that is a very handsome watch, but if you like the blue, my vote is for the Omega.
Between those two watches, I choose the Seamaster. That blue on the Rolex is just way too bright as @speedy57 said.
The Rolex is white gold IIRC. Seems like it would be foolish not to buy it if it was the same price as the SMP.
I personally dislike Seamaster 300, so would not buy it for sure. Smurf I had the chance to try myself and blue is very dull and milky without any depth to it. So would not buy it as well!
Although i highly dislike the He valve of the new Seamster, even at the same price point i would probably go for Omega. I must admit i never held this blue Rolex in my hand so it makes any kind of judgement a pure speculation.
Not feeling the blue hue on the Sub, but the build quality on Rolexes have always felt better to me. Also, the He Valve is pointless for the average user, analogous to a giant racing spoiler on a street car
Would only got me thinking of if the choice would be blue 41mm DJ with fluted wg bezel on jubilee bracelet vs. Omega Globemaster in blue. But here clearly the SMP