Which sleep option is better for your health: 1.) Sleeping irregular hours but getting more sleep overall from catching up whenever you can OR 2.) Sleeping on a consistent schedule but getting much fewer hours of sleep overall?
In order to answer this question properly, I'd need to understand what is "more" sleep, and what is "fewer hours of sleep". I guess what you mean is that both measures are relative to the other, but the answer would depend on what the difference between the two is. Sleeping irregular 8 hours is probably better (i.e. smaller risk for developing disease or worsened wellbeing) than sleeping consistent 4 hours, but 8 hours of irregular sleep may not be more beneficial than 7 hours of regular sleep. It also depends on how regular or irregular your sleep is. For example, changing your bed- and/or getup times by 1 hours from day-to-day is unlikely going to affect your wellbeing or health, whereas changing it by more than 3 hours, it may. It is important to note that sleep architecture (i.e. sleep stages) exhibit circadian variation, i.e. depending on what time-of-day or more accurately the phase of your average circadian clock, you will have a certain propensity towards specific sleep stages. As an example, if you sleep during the day (for instance when you hit your bed earlier, sleep in, or have a nap) you may have a different sleep architecture (usually less REM and/or slow wave sleep, and more light (NREM1 and NREM2) sleep, than when you would sleep in sync with your circadian clock (at night). The phase of your circadian clock is affected by your usual bedtimes, so one may say that if you sleep outside of your regular sleep periods, you are sleeping out of sync with your circadian clock and therefore your sleep has different architecture, which may be less restorative. I would like to add the extend of the impact this may have on your overall wellbeing and health, but I do not know.
I hope this answer helps you answer the underlying question you may have.