Keep the SERK, put the money for an ESP contract in an interest bearing account or CD rather than buy the ESP. If you have problems down the road, use the cash to repair the bike. If you don't have problems, the cash will be there to place toward the next bike.
That would have been my advice to anyone prior to the 110 fiasco. Now it comes down to how much you trust the MoCo to do the right thing if your engine fails shortly after the factory warranty expires. I'm not necessarily talking about the things covered by the "upgrade" program, since they should take care of those items, but something like a crank failure would more than wipe out the cash. So it really comes down to my favorite Dirty Harry expression, "Do you feel lucky?".
Jerry