clearstream
(He, Him)
My approach is pragmatic. I feel like I can offer greatest diversity when I can use both. I don't have to have 6-8 encounters. I'd like to sometimes have 6-8 encounters with a mechanically meaningful connection between them. There is more than one way to achieve that, but a simple way is resource management i.e. where PCs don't replenish all their resources between encounters. As [MENTION=6691663]Tobold[/MENTION] observes, that situation also better diversifies class features. The simple example is the Warlock. If PCs always long-rest between encounters, a level 10 Warlock will really feel the pinch of only 5 slots. If PCs more often short-rest between encounters, those slots have more value.
I feel like the pressure you describe is fuelled by a mismatch between rest and campaign scale. Say I use the Gritty Realism option from the DMG. I can then indulge a great deal of wandering by the PCs. The standard 8-hour long-rest puts a pinch on that because my party will likely feel they can take a long-rest most calendar days and as you observe I might then enjoy less narrative freedom. It's important to stress here that we're not trying to get rid of the single deadly encounter that challenges a fully-tooled up party. We're trying to broaden that by ensuring we can have meaningful easy and medium encounters too. And of course, there should be exploration and roleplay. "Easy" narrative encounters need no mechanical import, to be valuable.
I agree with you that class-versus-class balance in 5e is more even at every level, whereas in earlier versions of the game some classes were stronger earlier and some later (notably the martial-versus-arcanist balance). I don't think AD&D achieved it's intended balance as successfully as 5e does, and with the benefit of hindsight I'd likely argue now that cross-level balance was a problematic approach. Looking specifically at rests, I agree with you that 5e balances classes against 6-8 encounters between long-rests. They emphasise that ratio in the DMG and you can see it in the power-balancing of class features.
For me it is as simple as comparing the list of what I can offer with meaningful long-rests, and what I can offer without them. There are good things on both lists, but there are more good things on the second list than the first.
