Be careful, 
What the paste manufacturers recommend in terms of reflow profile has little 
to do with soldering, but a lot to do with their flux formulation. Its a 
cart-before-the-horse situation.
RSS [ramp-soak-spike] should always be preferred, but particularly for the 
higher T's needed for SAC-soldering, because it minimizes thermal gradients, and 
thus warpage. There is really no redeeming recommendation to be made for RTS 
[ramp-to-spike], unless your assembly only has lots of small parts of roughly 
the same [thermal] size.

Werner



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