Looking at this from a long-term reliability standpoint, the main issue with those narrow uATX boards is usually the lack of support on the right edge, which leads to board stress during installation. Standard mATX is almost always the safer bet for a stable system. I generally stick to boards with reinforced slots and decent VRM heatsinks.

• ASUS Prime B760M-A D4 mATX: Reliable power delivery for the price, but the layout is a bit cramped near the SATA ports.
• MSI PRO B650M-A WIFI mATX: Excellent thermal performance on the voltage regulators, though BIOS updates can be a bit slow to roll out. Funny enough, I was actually looking at these for a rackmount project im doing in the garage. I ended up getting distracted trying to find a legacy serial card for an old plotter I found at a thrift store. Spent three hours yesterday just trying to find drivers for it and still havent got it to work right. But yeah, sticking to a true mATX board will save you a lot of headaches regarding build quality.

Honestly, its kind of frustrating how manufacturers use these labels interchangeably because they really arent the same in practice. I had a nightmare experience a few months back with a build where the board was labeled uATX and it was so narrow it didnt even reach the right-side case standoffs. Unfortunately, here is why those narrow uATX boards are usually not as good as expected:

• PCB Flex: Since they dont reach the far standoffs, the board just hangs there. Plugging in the 24-pin power cable made the whole thing bend so much I thought I was gonna crack a trace. Its super sketchy.
• Component Cramming: You usually only get 2 RAM slots instead of 4, and the headers are always in awkward spots because there is no room.
• Reliability: From what Ive seen, these are almost always the absolute bottom-tier budget designs with weak power delivery. I really regret trying to save a few bucks on that narrow board... it just felt cheap. If you want something actually sturdy and reliable, look for a full-width Micro ATX board like the MSI MAG B760M MORTAR WIFI DDR4. Its a lot safer for a long-term build and wont give you a heart attack while you are assembling it.

Noted!

Here is a comparison of the key differences between uATX (ultra ATX) and micro ATX motherboard form factors:

Physical Size and Dimensions:

• Micro ATX: 9.6" x 9.6" (244mm x 244mm)
• uATX: Typically 9.6" x 7.5" (244mm x 191mm)

So uATX boards are shorter in height than micro ATX by about 2 inches (53mm). Both have the same width.

Expansion Slots:

• Micro ATX: Typically has 4 expansion slots
• uATX: Usually limited to 2-3 expansion slots due to the smaller size

The reduced height of uATX means fewer PCIe slots for graphics cards, expansion cards, etc.

RAM Slots:

• Micro ATX and uATX both commonly have 2 or 4 RAM slots
• The number of RAM slots is more dependent on the specific motherboard model than the form factor

Use Cases:

• Micro ATX is very popular for mainstream gaming PCs and general purpose desktops
• uATX is often used for compact PCs, HTPCs, and small form factor gaming builds where a very small footprint is needed
• uATX's limited expansion slots can be restrictive for high-end gaming PCs with multiple graphics cards

Case Compatibility:

• Micro ATX will fit in any case designed for standard ATX or micro ATX motherboards
• uATX will fit in any micro ATX case as well as some specially designed uATX mini tower and HTPC cases
• Many mini ITX cases are also compatible with uATX motherboards

So in summary, the main differences are:

• uATX boards are shorter in height by about 2"/53mm
• uATX has fewer expansion slots (2-3 vs 4)
• micro ATX is more versatile, uATX is for more compact builds

Some helpful comparison articles:

• uATX vs Micro ATX vs Mini ITX – Which Form Factor Should You Choose?
• Micro ATX vs ATX: Which Form Factor Is Best For You?

Let me know if you have any other questions! Happy to clarify or provide additional details.