Now that people are starting to finish the game, and since many of us have already long since played and finished Infamous Adventures' version of King's Quest 3, it is only inevitable that comparisons be made. I'm not posting any puzzle spoilers or anything, so have no fear of that. I'll give my two cents of the games, and invite others to do so. I'll go element by element.
Gwydion/Alexander: It was a tricky one. Both games do a good job, although IA makes him look well-dressed for a slave. Redux does a better job on the voice and clothes, although it is pretty much the same otherwise. The dialogue for Alexander in Daventry was much weaker in Redux than in IA, though. Redux still wins in my opinion, though, as the other dialogue was really good.
Mannanan: Each game handles him very differently. Redux portrays him in a manner closer to how the manual of the original described him, as a frail old man whose appearance of frailty ends when one sees his eyes. IA's version depicted him as a large, towering figure, appearing not only physically tall, but also magically powerful. While I kinda liked IA's version more, I have to give points to Redux for the more accurate depiction according to the manual.
There was one bit that IA did that I wish Redux had done. When Mannanan goes on a journey, it begs the question "Where does he go?" While there is no right or wrong answer (Shapeir?), IA shows Mannanan visit his brother Mordack in a cutscene located on Mordack's island, only referred to as "elsewhere." It was a chillingly good scene.
So, much as it is hard to decide, I just barely give this one to IA.
The 3-Headed Dragon: Redux wins this one both hands down, by far. IA's version looked like a pint-sized King Ghidorah, which, while dangerous, lacked the sort of kingdom-shattering menace required; IA's dragon was even smaller than the one-headed dragon from Sierra's remake of KQ1. Redux's dragon was huge, unique-looking, and gave the impression of extreme power. Redux gets this one both hands down.
Endgame: This part fell flat for me. The whole section after the dragon is dead but the game is still not done was sorta... lame. Between the seeming helplessness of the "father", the lucky charms gnome, the mooning bit from the original game that IA wisely left out, and the green pinball of salvation, the effect was less than stellar. Even so, if one suspends disbelief in the "pinball" sequence, it looks rather nice.
Still, IA gives the game a more balanced ending, no need to run an obstacle course, and shows that it took time for Daventry to rebuild, which strikes me as working much better than the pinball. IA wins this one. It almost makes one wish Alexander had stayed behind in Llewdor and become a benevolent wizard in some sort of "what-if" story.
Easter Eggs: Well done by IA, but VERY well done in Redux. I'm not giving these away.
Spells and Magic lab: IA did a good job with this, although the whole "you mix the ingredients" bit was rather quick. Redux gave a much better show of it. Also, the lab really gives off a hellish impression from above. I'm not sure if that was the intended effect, but it really does give the impression of Mannanan as a satanic figure, laboring away in a room of evil.
Cat Transformation Sequence: IA did a good job of it, but with Redux it was like... PWNED! Really well done, although I'm not sure the "fake choking" bit at the start was necessary.
Pirates: IA kept very close to formula with this, and while it was good, Redux did a fantastic job, although the island was a bit tricky. Still, once solves it, one solves it for good. Also, that first mate must still be in that town.
Time Limits: The original game and IA (if memory serves), placed time limits on a lot of things, notably, when Manannan would kill you, even if you had done nothing wrong. That those limits are gone in Redux is excellent. The warning timer is a novel and, in my opinion, excellent means of dealing with the limits here, although it seems to require repeated theft of the porridge (okay, minor spoiler). Good thing the bears keep making more bowls of it and they don't think to lock the door until after it no longer matters.
Oracle: Both IA's version and Redux do a good job, but I have to give this one to Redux, which approached the matter in an original way and made the Oracle into an even more mystical figure than IA did (or maybe even could, given their budget and smaller staff).
Introduction Sequence: Both of these are very similar. I don't know if there was any collaboration between IA and AGDI, but the similarities are pretty strong. Both were well done, and I can't say I know which one I liked more. Both begin with a sleeping Gwydion and an account of how Alexander was stolen from his real home, although both handle the specific differently. Redux's version is darker and colder, but IA establishes Mannanan as EVIL from the introduction onward.

Medusa: Redux put a whole new spin on this part, while IA stayed more or less with the original. I liked Redux more, although I have to get the better ending with her. Will do so shortly.
Abominable Snowman: Redux wins this one hands down, although it is not too hard to figure out how to do it, given how few other options one has. IA kept straight with the formula. In the tunnel sequence, again, Redux wins, although it takes a moment to figure out which tunnel NOT to take. XD
Music: For the most part, the two games are even in the music department, although Redux does a very good job at referencing music from KQ2VGA+. I'll give this to Redux, but barely.
I will give IA one minor "win" though; the mountains in IA felt much more arctic, what with the snow effect and the greater sense of altitude in IA's version. Still, the Yeti and the tunnels were the crux of this part, so Redux wins it.
There's probably a lot more, but I'll just leave it as it is for now. I thought KQIIVGA+ was a better game, with a much more fleshed-out plot and a better setup. The whole "father" plot line just fizzled in Redux, although the game itself is very good. If I had to choose, I would say King's Quest III Redux was the better game of the two KQIII reamakes, despite a weak ending.