The one on the left is built to last longer, and is practically timeless. The one on the right will probably fall apart after a few years of use, and eschews fucntion for a more "modern" design that will inevitably fall out of style.
(Please correct me if I'm wrong about any of this.)
As someone who's moved a several tons of the furniture on the left, I'll take the shit on the right all day. Not only is the shit on the left always incredibly heavy, it's also ugly as hell and takes up an ungodly amount of space
May have mixed feelings about the "timeless" bit, depending deeply on how it's meant. Do I think you'll find a buyer at any given time in the foreseeable future? Probably, yes. But I would have very mixed feelings about having that in my house. (Space consumption, cool on its own to some degree but clashing with basically everything else and cherubs are not my jam, maybe a status symbol since it isn't the norm.)
I have some ikea pieces that I bought when I started grad school. They're 10 years old, have been through 4 moves, and they're still doing fine. Even better, I could move them myself without it being a huge strain. They aren't high quality (which tends to seem to mean heavy and not disassemblable), but they've treated me pretty well.
Ikea’s stuff is fine for the price you pay. Oddly enough their solid pine items are really sturdy and usually among the cheapest since it’s so simple and comes unfinished. I have a Tarva queen sized bed and it’s great, plus I bought $8 of 2x2 and made custom length legs for it.
The one on the left wasn’t necessarily built to last longer. It was probably absurdly expensive back in the day and there were plenty of more cheaply made(but admittedly solid wood) options. No one is taking pictures of those less flashy pieces, though. Also you say timeless but, c’mon, it’s cool and all but definitely doesn’t fit everywhere. It screams “medieval castle” and is pretty over-the-top for basically any modern home, even grandma’s place.
The other thing about those shelves is that they’re a lot lighter than solid wood. When you want to place them in fun locations and need to use drywall anchors it’s a big thing to reduce the weight where you can. It’s not like people are displaying bowlingballs in them. They last a plenty long time unless you have a habit of trashing your place and there’s certainly such a thing as “over-built”. If that shelf “inevitably falls out of style” then style moves slower than I thought because they’ve been making and selling that thing for-fuckin’-ever. Most importantly it’s affordable in today’s world where executives have siphoned away all our money and the working class has been left without the funds to invest in quality furniture when the Ikea stuff does just fine.
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TL;DR the piece on the left was not common when it was made and the piece on the right has its merits, not least of which is accessibility.
One on the left is very sophisticated and whoever made it, definitely put in countless hours sculpting it. People downvoting thinking the one on the right is better are batshit insane.
If I want a work of art the left one is nice, but if I just want a fucking shelf you're insane to think it's the better option there. You really can't compare the two, they serve completely separate purposes