Hey Artemis.
As you can tell, the "Previous Editions" board doesn't get much traffic.
I've been playing Shadowrun for 25 years now and, in my opinion, the rule mechanics have improved with each edition. (The flavor/tone of the game world is a separate question.) I have liked each edition, and I'll be the first to say that 5th Edition isn't perfect and could be improved, but I still think there's been an upward trajectory in the quality of the game mechanics over the years.
(Others will certainly disagree with me. If you were to post this question on Dumpshock - a haven of traditionalists - half the responses would say that SR3 was the pinnacle of the franchise while the other half would argue for some hybrid of SR4 and SR5.)
There is relatively little than I prefer in SR4 over what's in SR5. Again, this is all my opinion of what improved in SR5:
+ Chargen is harder to optimize (this is good)
+ Initiative is more fluid, with more Interrupt actions to add strategy
+ Spellcasting is more balanced (Stunbolt is no longer an automatic "I win" button)
+ Decking/hacking is better defined
+ Armor has been simplified while damage codes are better balanced
+ Limits help keep a lid on dice pool inflation
From SR4, some of the things I miss include a handful of adept-specific powers and optional rules. I prefer SR4's approach to Advanced Lifestyles over SR5's. Some people prefer the gear prices from SR4, especially when it comes to hacking/decking. Technomancers have taken a significant step backward in SR5, which is unfortunate. Mystic Adepts took a giant leap forward in SR5, going from broken (useless) to broken (too useful).
I really enjoyed SR4 while I was playing it, but I would never go back now that we're on SR5. Again, SR5 has plenty of opportunities to improve further, but on the whole it is still a significant improvement (in my opinion).