if you had to choose between those 2 feats for your pure rogue build which one would you choose

i have a 13 rogue/3 fighter

i am trying to stay absolutely pure with my halfling rogue

feats are/will be:

(1) least dm of healing

(3) weapon finesse

(6) twf

(9) lesser dm of healing

(12) greater dm of healing

(15) idk, either improved twf or improved crit: pierce

IMO those dm's are great for self-preservation when you have less than 250 hitpoints

i do not want to take a level of fighter, but i may have to go 13/3 & just lose one rogue feat & one sneak attack roll

any advice would be appreciated as i am almost level 6

thanks in advance