I don’t know for sure if they are brave or not, because I can’t get into the mindset of a suicide bomber to really understand what he’s thinking. But I’ll give you my take on it anyway…
I don’t believe religion enters into the equation. Or not much, anyway. I’d say it would be pretty brave of a devout Christian to throw himself in front of a train to save a child on the tracks. Does it matter that he knows he’s going to a better life every bit as much as a jihadist does? I don’t think so. If you think that the belief in an afterlife lessens the bravery of a life-terminating act, do you therefore believe that athiest soldiers are braver than Christians or Muslims? I don’t think so.
I think the comparison to spree killers is closer. Jihadists are essentially brainwashing themselves into committing these acts, through being taught hatred and extremism and coming to seriously believe that the mere act of blowing up infidels is a glorious way to go out, regardless of the religious overtones. After you hate enough, and obsess enough, your brain must get to a point where nothing really matters, other than expunging that hatred. Thus a normally meek kid will work himself into a state where he can wander the halls killing people, and face down a hail of bullets from cops without flinching. There’s nothing brave about those actions - they’re the product of a form of temporary insanity.
Psychologically speaking, I imagine the rituals that suicide bombers go through play a part in this (note that the Kamikaze in Japan were highly ritualized and rigid, and their indoctrination/training bears a lot of resemblence to the way Jihadists are trained). The ritual helps put your mind in another state and create a form of mental detachment.
Most military forces around the world use the same kind of techniques to make their soldiers more willing to take orders and to be in a mindset that puts self behind their buddies, their unit, their country. Not the hatred and extremism part, but extreme physical training, mental duress, rituals, and being mentally conditioned to have a strong desire to live up to the standards of your buddies and unit.
I imagine some suicide bombers are brave. I imagine a few of them have second thoughts, but know that there’s no turning back, and they tremble and quake with fear as they reach for the switch. That doesn’t make them admirable, or sympathetic - it just means that they committed their particular act of evil in a brave way.
But I’m equally sure there are many suicide bombers who just hate so much, who have had their minds so twisted over the years, that they’re grinning like Cheshire cats as they flip the switch, ecstactic that they’re finally getting to kill the people they’ve wanted to kill so badly for a long time. They’re not brave. They’re sick and twisted. And another bunch who do it out of religious fervor, and they’re not brave either.