*Caveat on R5: I really don't know why people on these boards usually seem to prefer R4-D6 as their choice of 1-point Astro for Biggs.
Getting 3 or more uncancelled vanilla hits (no crits) feels to me just about as likely as getting a Ship crit of some sort. And R5 will flip it for free, no Stress induced.
Maybe I'm biased by the fact that I have already had Biggs live a turn longer twice, thanks to flipping Direct Hit on one occasion and Major Hull Breach on another, heh.
Because I've had games where Biggs should take 4 damage and instead only takes 2, which is much better than potentially flipping a crit down. It only preserves Biggs if you do flip down a direct hit and you can get rid of that by popping the droid - at that point it's no longer worth it as you can't prevent two damage and he only has 2 hull left.
In fact, I've had the droid stop 4 damage in one turn doing that - Biggs was left with hull and his astro rather than being, you know, dead.