We all have different sleep needs, and while some people really can live a healthy life with less sleep than others, there could be more going on here.
Feeling better after less sleep - including after getting less Deep or REM sleep - could be the result of our body trying to compensate for sleep deprivation. To do so, it releases stress hormones the next day and evening, giving the sensation of alertness. However, this natural upper comes at a high metabolic cost, and eventually the need for sleep reasserts itself. Often, the crash comes hard and fast. If you are switching your sleep patterns frequently - or notice that your threshold for a good night's sleep is rather low - you may notice that the day after having little sleep you feel energetic and alert but after "sleeping in" the next day, you feel grumpy and fatigued.
Furthermore, waking up from sleep the night after staying up all night long - or after a night of broken sleep - is often followed by grogginess the next morning, not alertness. This effect occurs because the circadian rhythm is still out-of-whack and also because the total sleep debt may not have been repaid. This usually normalizes the next day once we re-establish a regular sleep cycle, though this could take longer if your sleep habits have not be regular for quite some time!
Try getting a consistent amount of sleep every night throughout the week to determine how much sleep you really need. It can be impossible to determine your unique sleep requirement if your biological clock is always recovering from sleep restriction and followed by erratic make-up sleep.