One similarity I can think of is that neither are what you’d call an easily renewable resource. As their numbers increase, so does the likelihood that the means used to procure their sacrifice become slightly less than voluntary; intense moral pressure, outright indoctrination and so on.
This is obviously well established on the Islamicist suicide bomber milieu, along with stuff like handcuffing the car bomber to the wheel, but I don’t think this is happening in Tibet right now (where the 91st self-immolator went up on Monday), and there’s nothing I’ve heard about the demographics of the protestors that indicates any sign they were the selected on the grounds that they had pre-existing suicidal tendencies or were easily influencible in that direction. But if people keep self-immolating at the current tempo then the numbers of actual volunteers are going to run out, which in turn means either stopping or establishing a production line. And there’s also the fact that most self-immolators are from the Tibetan parts of China rather than Tibet proper, in areas which have seen both an unprecedented level of repression since 2009 and a programme of forced settlement of semi-nomadic populations, a combination which tends to produce a larger number of volunteers from a smaller sample group.
And in view of stuff like this it all seems so futile.