That's true, it depends what stage though, like, on a stage with a high ceiling like FD, I wouldn't put too much faith in Utilt to do the job at a reasonable %. It's true Utilt is an underused move compared to Bair, since Bair can be used for spacing and even edge-guarding. Utilt is the fastest tilt Ike has, so using it as a KO move makes sense, but I've found Bair can KO earlier, even if it's worn down a bit.
I think it all comes down to situation. Sometimes Utilt is better as a jab follow-up and sometimes Bair is better. My problem is that I play mostly online, so it's extremely difficult to vary my jab game effectively with the input lag. I cherish the few live tournaments we have here where I can play to my full potential (which still isn't too much right now...)