I use Sleep mode on my Desktop and Laptop's since I run unattended daily overnight scans and I can wake the PC's with Task Scheduler.
I do encounter an occasional issue with the Sleep mode on my Desktop when I invoke the Sleep mode but it's infrequently intermittent and not causing any issues at present.
I haven't as yet encountered more significant issues as many have, according to searches about the topic, BSOD's at wakeup, lockup's at wakeup, etc.
I'm using S1 Sleep mode on my Desktop PC and Hybrid Sleep S3 on my Laptop.
As far as what's best for the hardware, as mentioned, it's a widely diverse topic. Powering up any hardware can increase the chances of voltage surges but that's true with anything, appliances at home, etc.
If I wasn't running unattended tasks overnight I might be doing the same as others have recommended, shutting off the Desktop at night.
One advantage that I like with the Sleep mode is that it's fast way to resume PC activities vs booting up after a power-up. I don't use SSD's so that also factors into my preference to use the Sleep mode since my bootup's will require longer with the conventional HDD's.
I have "hibernate" disabled on my Desktop since I always close any apps, activities before invoking Sleep mode.