So, the choice is yours: you can die with one, or you can die with the other. 'Course, you could really take a walk on the wild side and go bare.
Then there's always the belt + suspenders type, who'll want to sign up with both services. My take on FinalPartings.com, which does offer a choice of venues to deliver the news, is this: though it offers a lifetime subscription, alas, it's the company's lifetime that concerns me, not mine.
I am reminded of Alcor and all the rest of the cryonics companies, which you pay to keep your body frozen in a tank of liquid nitrogen forever. That's all well and good, until somebody forgets to make sure the emergency generator's charged before a massive power outage.
That's a lot of expensive fertilizer in those tanks. And, like Soylent Green, it's people - namely, you.