Apple Watch Series 3 vs. Series 4: Which one should I buy?

Fall detection will not be automatically enabled if you have entered your age when you set up your Apple Watch or in the Health app and you're age is less than 65.

Regardless, there is an option to manually enable or disable fall detection

More on this here: https://support.apple.com/en-gb/HT208944

I’ve got the same question, how is the performance of Voiceover on the series 4 VS series 3? I had a series 0 and sold it around th time watch OS4 came out due to its lagginess. I’ve read that the series 3 is much more responsive, but there’s still lag between VO sounds and speech, how does VO perform on the series 4 in this regard?

I spent a very brief amount of time looking at an Apple Watch Series 4 this morning, and VoiceOver appeared to be much more responsive on the Series 4 than it is on my Series 3. So, if you can afford the Series 4, I would definitely recommend getting it... As VoiceOver responsiveness, at least when flicking around the screen (which is all I really tried), is significantly better on the Series 4 than it is on the Series 3.

Hi.
Of course you should get the series 4. I don't see any reasons to get the older models.
In Watch OS5, Voiceover is even more responsive on my series two, which is very much welcome. I was pretty much giving up on the Apple Watch in OS4, because I found Voiceover to be very slow and frustrating to use. But Watch OS5 have made me use the Watch for more things.

Coming from a Series 1 and recently updated to a Series 4, I agree with Michael that there is a definite improvement with VoiceOver performance. I haven't updated my Series 1 to Watch OS 5, so I would be curious to know how it performs with VoiceOver.

But going back, if you can afford the newer Series 4, then I would strongly recommend it.