Note: X Chance only works if you're doing HP or Lust damage. They have effectively 0 chance if the target still has Shields/Armor, unless they're at least partially Lust weapons (though Lust weapons are useless vs Robots). Special Status attacks (Headbutt/Paralyzing Shock/Concussive Shot/Etc.) work through Shields/Armor.
MedImplants are good if you expect to take damage. I'd suggest you experiment with both to see how much damage you're likely to take.
There are a handful of things that bypass Shields, so if your class doesn't have innate healing, MedImplants might still be worth it. Or you could make a Vampiric Custom Psi Weapon.
I'd generally recommend
Medical Milkers over MedImplants because of the bonus to Max HP*, unless you really don't want your Steele to lactate. It also makes Hand Milk masturbation restore health, if you have at least 100% Fullness. If you're worried about not being able to heal when you need it,
Milkmaid's Aid is cheap and stacks to 50.
*Which also boosts % heals like Second Wind/Psychogenic Vim/Tike.