Rejuvenation Bead or doran's shield?

Well with the dorans buff i would say

If you are playing someone who is building Tiamat, always get 3 rejuv beads. You Regen so much more, and you only lose 90 gold from selling the two rejuv beads you don’t need, compared to the 210 which you lose from dorans shield. Against poke lanes it is godly.

if youre squishy but with poke, Doran, if have free tanky stats ( cough) 3 Rej beads might be good as long as they dont disturb your purchase equation.