Should I upgrade iPhone 5S to the latest iOS?

I've just got an iPhone 5S and I don't know whether I should upgrade it or not. I've read articles that say it'll be much slower, what do you think?

No- its fine

If you are happy with what you have now then stick with it.

I've seen no performance issues after upgrading.

Update it to the latest iOS Software. IPhone 5S can still run fast.

No, switch to Android if you can I have heard ios 9 lags.

Too many potential problems with upgrading the operating system in a phone it was never designed for. I you want all the benefits of iOS9 get a new phone such as iPhone 6s.

The 5S can use the latest iOS with no noticeable slowdown. The only place you might see a slowdown is in using some of the newest apps that require iOS 9, but they slow down the operations of any iPhone model. They are simply memory hogs that use lots of the iPhone's resources. Some of them were actually designed for iPads, but because the iOS is the same, can be used on iPhones as well. Now if you were talking about a 4S, that would be a different story, as it had a much slower CPU. It can also run the latest iOS, but is incapable of running some of the newest apps and features simply because its older ROM wasn't designed to handle them.