factory data reset after oneui2.5

there no need to this..... just clear cache from boot loader menu

no need only you should do is wipe cache partition

after you update one ui 2.5 i think It turns out that there are a number of times where it can be beneficial, but in most cases it’s certainly not necessary before the update. In fact, what we’ve learned from our research is that a factory reset can often fix any residing problems, but the reset should be done after the update has completed and not the other way round. Things such as battery drain issues, LTE & Wi-Fi connectivity problems or sluggish behaviour can often be fixed with a factory reset if the update did not resolve these issues already.

If you find that your device is running smoothly without any hindrance after the update, a factory reset is absolutely not necessary.

So in summary, a factory reset before an update is not necessary. A factory reset after an update can be beneficial.

The result will be beneficial but it can do some good after an update has been completed. You may find it is best to enter your recovery to do a full wipe of your cache partition to get rid of any unnecessary data from the previous update.

ya go a head for any huge update u won't get bugs

first of all if you install that big firmware simply by mobile data or wifi then it's not process...that firmware needs to be flashed by odin or through authorised samsung service center as they use odin only for their official purpose or via smart switch and pc.... otherwise if by chance software loop hole comes by simply update then anything mysterious can be happened with device in that case factory reset not sufficient..... remember allaways try to flash software for any big os or new ui interface which is proc3ss because samsung provides non A/B partition type ota software not like other company hence mobile data or wifi can create anything unexpected to device