Thats not going to help your issue but feel free to waste your time doing so.
I don't know what world you live in, but it's a valid troubleshooting technique in mine to try someone else's software out on the same hardware when available. Certainly saying nasty things to someone is
not going to help his problem. That much is certain.
Im not sure, i have not heard to many people that are having your issue. All i know is its not an OS bug, which leaves the wifi chip or router incompatibility issues.
You can't
know that either because OS specific bugs CAN and ARE often only problematic on some machines due to different drivers and hardware (and yes drivers are damn well a part of the OS). Ironically, the two things you do suggest as potential problems
can be tested using Windows on the same machine since it will have a different driver (i.e. if it works fine in Windows, then the problem most certain IS in OSX, either in some configuration file or the driver itself). Certainly, I have had hardware problems with OSX versions that were solved by either a software driver update or an update to an onboard chip configuration (flash update).
My current 2012 Mac Mini will sometimes connect to WiFi on a reboot and give an error ("Not connected to Internet" but connected to the 5GHz channel). If I select the 2GHz channel and then go back to the 5GHz one or turn WiFi off and then back on, it goes away. This will not happen if I remove the Ethernet connection and run with only WiFi and it doesn't happen on every reboot either. It's clearly an OSX problem and likely a timing one at that given it goes away upon re-connecting to the same channel. And yes, you can have both running at the same time with the faster one set priority (separate addresses and some software can use dedicated one or the other such as Apple's own "Maps" software that requires WiFI to get a location fix, which is why I have them both run as my Gigabit Ethernet is faster, but options like location tracking in Maps is handy).
It also never seems to happen on my 2008 Macbook Pro even with Ethernet plugged in and prioritized the same as on the Mini and both running Mavericks. My Mini couldn't go to sleep (except manually) with Mountain Lion and couldn't properly wake from sleep sometimes with Mountain Lion. The 2008 MBP had no such issues in Snow Leopard or Mountain Lion. Mavericks fixed that problem on the Mini and it now sleeps correctly (although OSX in general won't recognize NFS as a valid network "do not sleep" token and thus I can't use sleep even so since I have an XBMC powered older AppleTV that is using NFS and the Mac will go to sleep while it's playing a video). I've given Apple feedback and they ignore it.