Main application is getting a USB monitor to the front edge of my desk with my drawer keyboard and mouse setup. Stands permit easy reorientation.
A laptop alternative can have better performance with discontinued products, need a hub, and take up useless space with keyboard and trackpad, with monitor further back then I want. 2in1 flip laptops all suck at graphics/gaming. Laptops with "good" gpus will get loud, and right in front of you. Display shakes when you type.
A desktop means more clutter under desk, but, as with laptop, need a usb hub, and it seems hard to find one with even usb 3.1 (dp alt mode) that allows powering usb monitor with single cable.
laptop advantages include ups, doing something in power outage, and transportable computing. minipc + usb portable monitor not quite as portable. Tablets and phones beat the portability need, but ups is nice, and then if I think its nice, I should get one for pc/mini pc.
desktop advantage is gpu per price, and unlimited storage expansion. mini pc with 780m is simply good enough gpu with much better cpu than competitive gaming PCs. APUs also allow for very high GPU memory allocation, that could benefit some games, but also compute applications.
seems like most miniPCs still need a hub/docking station for wired key/mouse.