You're very likely to receive pretty strong opinions both ways to this question, so I'll try to give you an overview of the things you ought to consider for yourself that might help you decide.
1. How often do you watch movies or listen to / watch material that could offer multi-channel content?
2. What size is your listening room? Is a Unitlite up to it? Is your rack big enough for the Pioneer AVR? (Make sure you measure depth front to back including a sufficient gap for all the cabling and ventilation).
3. Longevity: I've had my AVR for 3-4 years now and it's worked very well in the main (apart from the odd app glitch where an Apple iOS upgrade rendered the control app useless until Pioneer introduced a new app.). Traditionally AVR's tend to be outmoded more quickly than conventional stereo equipment with the introduction of new music or video formats. My own AVR is about to be affected by the whole 4k / HDMI 2.0 / HDCP 2.2 / Atmos (if you're interested) and DTS-X volley of updates that will gradually make it obsolete.
4. Set-up. AVR's are a LOT more complex to set up and get sounding right. I can make my own receiver sound fantastic or truly ropey depending on a raft of set-up options. So this impacts a couple of things: if an AVR sounds bad in a store, it could be that they've not set it up well or it could simply be bad! But how do you know? The other thing is that all the set-up tweaking in an AVR (full detailed equalization or room-correction software) can do things a straight 2.0 channel system couldn't. If your room is not acoustically problematic this might not be an issue for you, but it's worth factoring into your decision.
4 and a bit: Features. AVR's have tended to be more feature-laden than stereos, but in the case of the Unitlite the gap is narrowing. The Pioneer has Airplay and Spotify Connect but the Unitilite has Spotify and Tidal built-in now.
5. Sound quality. This is a hornet's nest subject, so decide for yourself. Some will say that all 2-channel systems are better and there is a certain cost/benefit analysis that makes this sound very logical, but there are others who will vehemently defend their AVR's being every bit as good as a 2-channel system. In my own experience my old stereo set-up was better timed and had more of a dramatic 'wow' factor with certain music but my AVR does soundstaging and piano beautifully. My AVR is more forgiving of more music types, but this could me more to do with amp/speaker tonal balance than stereo vs multi-channel per sé.
I've listened to good stereo systems and horrible shouty ones too, and some of those horrible shouty systems have been very expensive indeed, so this undermines some of the arguments aimed at AVR's vs stereo amps: higher quality components don't always mean you're going to actually like the sound more. I've heard some limp surround systems and some fantastic ones. Good sound is possible from an AVR, but you've got to get the right amp/speaker combo and the set-up spot-on. And some AVR's are more known for their musicality (Arcam, Marantz, Anthem).
I use my system 75-80% for music. I am happy with it, but I'd be lying if I said I'd never consider a 2.0 channel system in the future. But my AVR is SO much better at movies than my old stereo system that if I did explore 2.0 channel in future, it would be in addition to, not instead of my surround set-up.
My own feelings particularly considering built-in obsolescence and how good AVR's are at movies is that having BOTH is the best. I'd personally go for a midrange AVR with a good sub/sat package and be prepared to replace the AVR every 6-7 years or so, but have a stereo amp and speakers too that I'd keep for longer. Cost-wise this would be no more expensive than a high-end AVR. There can't be much more gutting than spending £2k on an AVR and realising it's out of date after a few years. My £500 receiver (marked down from £800) doesn't sound such a painful loss.
Go to a few dealers and listen for yourself. Sorry for the rambling. Hope some of it's helpful.
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