Kida are fun to play just because you're a strong bug dude. They are a scarce sight on the Cyberiad. For better or worse, people will notice you and you will most likely be memorable just for being one of the kidan players -- They're all pretty distinct and things like DNA scramblers and chameleon kits don't really work. Mechanically, the "no eyewear" thing is a pain in the ass if you play medical or security, but you can adjust with time in your own way or get implants. (As someone that plays a kidan that exclusively plays either sec or medical.)
Slimes are also fun to play because they're little goo people. They're a tad more common and fit into disguises much easier than Kida, partly because of their very human anatomy. They cannot be revived on death without quick recovery, monkey-man clones, cyborgification, or skilled doctors with a supply of mitocholide and strange reagent, which is really their main mechanical drawback. Slippery blood also causes a hilarious shitshow during an emergency, with dying people slipping where dying slime people came through.
Kidan customization is high-quality, and a bit more diverse than humans. You can change antennae, eyes (which make up a good portion of your sprite, mind you!), horns, and body accents (which affect your biolamp colors.) People seem to physically ID kida by eye color.
Slime customization is very human and limited -- The only real difference is you can change the color of your slime. This slime color is probably what people will ID you by.