Generally speaking, this is a highly restrictive aspect of owning an AIO compared with a traditional tower desktop. AIOs have much more in common with laptops; both may let you upgrade the memory or storage, at best. For some users, that's enough, but it's still not all that common for these mostly sealed designs. Like with laptops, memory or the SSD may be directly integrated or soldered onto the motherboard, meaning you're stuck with what you have. And CPU and graphics upgrades are a nonstarter.

End-user upgrades are just not a priority with AIO designs. Even if an AIO chassis does open up easily and its components are not soldered down, it's more like upgrading a laptop. An AIO may use mobile SO-DIMM RAM (possible to acquire, but not the same size as desktop RAM), and M.2 SSDs may be size-limited versus the full-size slots on most desktop motherboards.

With a traditional desktop tower, installing a graphics card into a system you originally purchased without one is at least an option (provided it has the space, the slot, and an adequate power supply). You'll never fit one in an AIO's interior, however. If substantial future upgrades are a priority or even a concern, an AIO is not the right pick. Get a tower-style desktop.

On the most basic level, one of the main reasons for choosing an AIO is that you don't need to buy separate parts, like a monitor and speakers. All-in-one PCs represent exactly what the name implies: a complete desktop computer in one package, delivering a plug-and-play experience. Your screen and components are all tied up in one device, like a laptop, which takes up less of your desk or floor space than a desktop tower and monitor combination.

Even if you find a laptop you like with a roomy 17- or 18-inch screen, you'll need a strong back to carry it anywhere; 6 pounds and up, plus an AC adapter, is typical for machines like these. We suspect you won't travel with a desktop-replacement machine like that all that much, which could make even a small-screen AIO a viable stay-at-home alternative. And because AIO desktops are plugged in, you won't ever run out of battery power.

Because AIOs tend to use more powerful processors than many thin laptops do, a well-chosen all-in-one PC could execute CPU-intensive tasks more rapidly, on the whole. Some 3D games will run better, too, thanks to the discrete graphics chips in some A-grade AIO PCs. To find AIOs with discrete chips, look for one of the few AIOs with graphics solutions dubbed GeForce RTX, as opposed to Intel Iris Xe, UHD, or HD Graphics, or AMD Radeon (no "RX") integrated graphics.

Other advantages? You can share the PC among family members and use it to store centrally accessible photos, music, and videos. And a large, widescreen AIO PC makes for a fine videoconferencing system. Rather than having the family crowd around your iPad or a little laptop screen during calls, seat them in front of a 27- or 34-inch AIO desktop so you're not subconsciously squeezing together to "fit on the screen." Plus, a large AIO screen is ideal for watching a movie from 5 or 6 feet away, so a couple in a studio apartment could use a big-screen AIO as a TV in front of a small sofa or loveseat. Or, if you place the system in a central location, such as your kitchen counter, you can monitor your children when they're online.

But these PCs aren't just suitable for play. A few years back, Apple brought the AIO further into workstation territory with the iMac Pro. The starting price for this monster machine at launch was high, at $5,000, but it packed a jaw-dropping amount of muscle: It had a 27-inch 5K screen and was configurable with up to an 18-core processor, 128GB of memory, and 4TB of solid-state storage. (Note that you may still find it for sale from non-Apple sources, usually used or as a refurbished model, but as of March 2021, Apple discontinued it.)

This kind of muscle is usually found only in elite-grade tower PCs. We haven't seen a brute-force AIO to rival the iMac Pro since, but today's top-equipped AIOs can rival at least a decently equipped tower desktop. Apple's homebrewed M-series chips in the latest iMacs mentioned are fast. And while many Windows AIOs trend toward the budget side, you'll find some models with quick processing options.

Of course, all-in-one designs come with some considerable limitations. If something goes wrong with the display, the fix is not as easy as swapping out the monitor, as you might with a standard PC tower setup. The screen is part of the package; the same goes for any component here. This is much closer to the laptop experience: When one part goes, it usually makes the system less usable overall. You're much more likely to buy an entirely new laptop or AIO when a part (or multiple parts) stops working well.

Sticking with the laptop comparison: While AIOs have bigger screens, you're giving up a lot of portability versus a laptop. AIOs are more portable than tower PCs, but you're unlikely to move your AIO once it's in place, apart from purpose-made models like the unique (and aptly named) HP Envy Move.

Compared with standard desktops, PC towers tend to have a higher power ceiling than AIOs. Most all-in-ones employ higher-end laptop processors, given their slimmer design and limited cooling, so traditional desktops contain more power potential. High-end towers are a much better fit for intensive work, like CAD/CAM or scientific data processing, and this is doubly true on the graphics front. AIOs lack desktop-equivalent graphics cards because of size and thermal concerns; the very few that have discrete graphics at all opt for laptop-level mobile graphics chips. PC gamers will get far more value and satisfaction from a stand-alone tower (where they can swap out a graphics card) than from a fixed-config AIO PC with much weaker graphics.

Crucially, all-in-one PCs lack the expandability of most towers, which is again related to their slimmer, more space-limited designs. This brings us to the next point.