Yes at first approximation they are the same, but the mechanism of the update is different since one can be a delta and self-applied update and the other installs a complete build rather than patching the OS.
Digging deeper, the OTA update implies the OS and device is working properly, so Finder or iTunes is a good bet if you really want to ensure the update goes well or want to put the device into recovery mode to ensure the new OS and only the new OS is written. Obviously, if the device is having problems, you may opt for a computer to control the update rather than hoping the device stages, installs and executed cleanup of the patch properly.
Assuming your device is working well, you can safely update OTA and in many cases - the download is a delta update that is smaller than the entire image if you are doing an update that isn't a major version (4.0 or 5.0 which started the OTA capabilities and presumably 6.0 when it ships).
Using Finder or iTunes also gives you a chance to transfer purchases and reduce the number of apps you will have to re-download after a major update. Again, not an issue on incremental updates like 5.1.1 update from 5.1.
In practice, this even has been called out as a deciding factor for the jailbreak that was first released for iOS 7 where the notes said the exploit won't work against an OTA iOS 7 device, and only against a cleanly restored device. I don't know if that has to do with the signing key or an actual difference in the two images, but it shows that the processes are indeed different in some respects.
Best Answer
Normally, if you have difficulties updating OTA, then you can manually fetch the updater, an .ipsw file, & run it manually from iTunes [Finder in newer macOS.]
If you are trying to update to the latest iOS, then iTunes will usually find the correct file for you. If, as in this case, there is a security update for an earlier iOS then you may have to fetch it manually.
ipsw.me contains lists of .ipsw files for all devices, going back into the mists of time. They do not store the content, merely the correct addresses to where Apple keeps these updates.
They are only useful for as long as Apple are still signing the update - usually a couple of weeks after the next update is released; the window of opportunity can be short.
If you download one of these, then in iTunes you Opt ⌥ click the Update button & you will be asked to choose a file to update from, rather than the automatic process. Once chosen, assuming it's the correct file & still being signed, then the update will proceed in the same way as any regular update.