No it's not Guess vs. Levi's.
Many SF settings have mankind trying to improve itself through genetic engineering. Friction arises between the uplifted and the plain vanilla humans and hilarity ensues.
Or war, open or otherwise.
One of the best takes on genetic engineering IMO and a great movie in all respects is Gattaca (1997). Genetic modification leads to a class structure which is hard to argue against. Most job interviews consist of providing a DNA sample.The smarter, stronger etc. candidates should get the best jobs, right? Everyone agrees that it's better to be better, right? Not quite.
First of all there's still a lot of unexplored territory in our genetic structure. These frail, cellulite ridden, alopecia plagued, appendix popping wrecks we walk about in are currently the result of millions of years of testing. There may be reasons for a lot of these drawbacks. Cure alopecia and maybe the subject acquires the gene for color blindness or schizophrenia. As I said in my post on felinoids we don't know the reasons, for example for humans being hairless or tailless. Perhaps your bod-modding crew makes themselves into man/generic mammal furries and discovers their new appearance and DNA sequencing triggers atavistic rages when they find that Guess jeans are not made specially for those with tails. Perhaps they discover their feline modeled upgrades give them perfect balance but throw their inhibitions to the wind on a regular cycle ("Dream on. Cat-guy don't know you're breathing ... but wait till the 14th. Hunh? Yeah there's an app tells you that stuff. I got it.")
Not all the drawbacks will be that obvious either (you wish). Genetic tweaking could result in a standard upgrade package provided to all citizens in the womb. This can have the effect of reducing genetic diversity. Now reduced genetic diversity usually appears in very small populations in nature. Like the 60 or so Amur leopards living. When you have low genetic diversity then any bacteria, virus or bug that one individual gets infected with has the potential to infect everyone. What one can't fight none of them can fight. Standardized genetic coding can result in true pandemics. Sure no big deal if it's athlete's foot but a new flavor of influenza is a real problem, especially in a closed environment like a space craft or station.
The last problem with genetic engineering I can see (I'm sure you guys can come up with many more) is copywriting. Let's say your company creates some individuals the make Khan Noonian Singh's supermen look like The Inferior Five. They are going to have kids unless you made them sterile. So your fantastic gene mods are going to be dispersed among the population. You might have to have them sign agreements not to mate with individuals below a certain genetic rating or just with people with similar tweaks but it isn't going to work. Humans will mate no matter what. We even got busy with our Neanderthal cousins and when you can close the deal with a person who can benchpress a boulder a slip of paper will not deter you. Also your gene product is presumably brilliant and probably brighter than whoever thought up the safeguards you put in place. Any genetic royalty is going to be subsumed eventually.
In evolution the race does not always go to the swift or the battle to the strong but it is definitely slanted towards those who keep churning out kids.