You're not getting the same depth of sound out of 1.5" - 2" speakers as you are even bookshelf speakers. Completely lack mid's. And having a sub trying to fill in those mids from a location that mids shouldn't be coming from sounds awkward.
Maybe it works for some people. I just didn't find any of them to be even remotely good.
Those HTIAB setups don't really have that much of better speakers. 2.5" and 4.5" usually, sometimes 5" or 6", mounted usually in a plastic molded enclosure, although sometimes you get MDF. The real benefit is that you can position the speakers out around and make a better sound field. The receiver may have better inputs and a bit more flexibility with the settings - but that isn't a given. I'm going to say "HTIAB" differs from "Sound Bar" in that the HTIAB solution has a discrete receiver and you could upgrade the speakers later on fairly easily.
Here's a typical one, at about $550 - it has 2.5" drivers and a 8" sub. That's pretty normal for the cheaper (<$1,000) Home Theater in a Box setup
Here's a competing sound bar. It's basically the sound bar up front and 2 rear surround speakers with a sub. 3.5 x 2.5" in the sound bar up front, 3" in the rear with a 7" sub. No discrete receiver though, so this is what I would consider a sound bar solution. In fact, all the "in a box" systems at Crutchfield are this style until you jump up to some significant money ($2k+)
Powered sound bar, subwoofer, and rear speakers with built-in Bluetooth®, Wi-Fi, and Amazon Alexa
www.crutchfield.com
You need to step up to a discrete home theater setup to get real significant improvement, and you could piecemeal upgrade a HTIAB setup if you wanted to - but that's much more money, and you're in a entirely different class of setup there.
If it's just a TV in the bedroom or kitchen or something - I'd say a soundbar is more than enough. It's going to be drastically better than the built-in sound on any TV, it's going to be easy to install and configure, and it will be cheap. If you are looking to do a home theater. well, then it becomes a matter of budget - just like if you are looking at putting together a PC for someone. I've invested quite a bit of money in my setup over time (not audiophile money, but as much as I have any computer build), but that doesn't mean I would recommend that to everyone.
