I like both the G1 and RiD2001 ones. Yes, G1 Magnus is a brick, but bruh, what a lovely brick it is. It looks imposing and like it can kick some serious ass. RiD2001 Magnus is much more articulated but still retains that imposing appearance. Plus, he can combine into Omega Prime.
RiD Ultra Magnus - the sheer amount of engineering and play value built into that monster is unbelievable! Huge robot that turns into a functional car carrier. With a sound pack that changes its clips depending on whether and how the giant gun in plugged in. And then he combines with Optimus Prime, and has an entirely different set of sound clips! Classics Ultra Magnus with City Commander armor. Bulky and powerful-looking. He doesn't match any particular official interpretation, but is FansProject's own take on the character. And it still hasn't been fully matched in my opinion. Only real downside is the big armor pieces can interfere with posing. Takara Legends Ultra Magnus with PE Core Magnus - less solid than the Classics set, but easier to pose. Fully functional as a car carrier. Came with a bonus WST Alpha Trion. Takara's version was already nice, but the PE addon made this guy nearly perfect - added in the albino Optimus core and replaced the chestplate with a blockier, slightly more G1-ish one. Siege held the best spot for a few months til I got the Core Magnus addon for Legends Magnus. It's great that we finally got an official albino Prime with exosuit, but he was let down by the smaller size of WFC leaders, the limited functionality as a car carrier, and fiddliness of assembling the trailer.
CW only because of my affection for Minimus Ambus and MTMTE. Removing him from the equation, it’s not an especially solid or great figure. Siege would be my pick for best based on being super solid and really fun to mess with, followed closely by Animated. Animated Magnus is simply a great toy, but it’s pretty far removed from the others stylistically so I’d almost leave it out.
Not mentioned here, but still a very good Ultra Magnus is the e-hobby G2 Magnus: A repaint of the Laser Optimus Prime, but in the colours of the full armoured character. Colourwise, the only thing I don't like about it is the blue being so dark. Much prefer the light blue of the G1 toy.
Quite a few, yes. And most (if not all) I also wouldn't count since they're just Optimus in white. But this one I would count since they went for the armoured colours, same as the Beast Wars Big Convoy repaint. And this G2 I think is even better since it still has the white truck.
I don't know about objective best, but the Combiner Wars one with Minimus Ambus is the one I went for, really like the Nick Roche inspired design and he's a suitably big lad.
BPF Siege Ko of Magnus. Fixes all my main issues with the seige figure at a better size and clean paint.
I'll probably get Kingdom Magnus if I have the chance and can afford him, but CW Magnus wins solely because his car carrier mode can actually carry cars inside it.
I’m going to have to give 2 answers: 1) As for Vanilla Prime versions of the character, Generation 1. Originating in Diaclone, it was one of the first concepts of a Prime with armor add-ons that we ever got. A nice way of adding replayability to the original mold. 2) As far as self-contained and non-parts forming versions go, my pick goes to Animated. It was a nice refresh of the character that didn’t feel compromised in any way.
Siege as it's the first and only UM figure that pulled me in as I love the armour approach and to me is the only "correct" way for him to be... it's biggest con is that they didn't design him to carry other cars, and second is the gaps that requires a proper kit to complete the figure.
I like CW then Animated then Netflix, but this is also interpretable as the order in which I have affection for assorted versions of the character, so make of that what you will.
^I love the MP version as well, but the OP is excluding it from the discussion for the purposes of “fairness.”