Can you choose which iPhone update you want?

Ok so I have a iPhone 6 and I only have 16gb and sadly I can't even really use all of them but I'm trying to conserve space and the new update 9.3 is out and I really don't want it so I was wondering if I don't get it and install will I still be able to download the next update 9.4?

You can easily choose not to update to iOS 9.3, when iOS 9.4 is out you can update straight to that if you want. As long as Apple are still signing the firmware, you can upgrade/downgrade to it. Why don't you want iOS 9.3 anyway? If you don't want that then I don't see why you would want 9.4 when that comes out either, it would be iOS 9.3 with a couple of new features.

Yes. I'm still using iOS 9, but none of the upgrades for it. I probably won't update, at least not for a very long time.

You don't have to update at all if you don't want to. And sometimes it's good to wait or not update depending on what kind of bugs are found in it or if it's a crummy update that makes your phone run slower or takes up too much of your limited space.