It's probably not necessary, not much of a difference between being on 9.0 or 9.5 for games.
There are games that use 9.6+ encryption but they can be cryptofixed to work on emunand 9.0-9.5
And then games that just require you to be on higher than 9.0 you can just bypass that requirement with fw spoof when making the cia (and if you're just downloading them online most likely they already have fw spoof on them.)
That being said, personally I'd update it to 9.5, just for the satisfaction of being on the latest possible firmware, that and 9.3 has added
some features to the home menu which you might be interested in.
imo an advantage to updating to 9.5 is, that's an additional thing that lets you tell if you are on emunand or sysnand. Since sysnand will probably remain at 9.0, when you are in system settings you'll usually see RX-E, but I've had it stay as Ver. sometimes and I don't know why (O3DS so i don't know if that happens on N3DS, but it doesn't affect functionality so that doesn't matter much.) But anyway, if emunand is on 9.5 and sysnand is on 9.0 then you know you are on emunand when system settings say you are on 9.5
Also there's another CFW which does not replace the Ver. string, so if you are ever interested in it (CakesFW), it's good to have emunand higher than sysnand so you can tell which one you are on more easily. Generally you -shouldn't- really accidentally end up on sysnand system settings if you have menuhax autoboot, but it's always good to stay on the safe side and have more visual cues.