New one is likely the best. Legends has better painted details, but the new one is very good for a Hasbro general retail release.
Let's face it, G1 Arcee was a design that was never meant to transform in the real world. Outside of Masterpiece complexity and pricing, we are always going to get Arcees that integrate vehicle mode parts and compromise the look of the robot mode, or prioritize the robot mode at the cost of being shellformers.
It looks to me like this SS86 version takes the better parts of the T30 and improves the accuracy of the robot mode, without being quite as shellformery as ER. Sure, it's a compromise, but I'm not sure anything better is possible at the deluxe price point without completely abandoning accuracy to one of Arcee's modes.
There was a time when it was "impossible" for Arcee to get a toy, now we get 2 or 3 every year. Crazy.
I think it shows also that Hastak listen to fans and that we don't need to buy new versions of characters if we find them lacking. We don't need to worry that a better release will take ages, as recolours and remolds for many characters seem to be more frequent than ever before.
That's why I'm still unafraid of passing on many Siege/Legacy figures (my first snubbed "collectors" line, excluding Animated, Prime and Bayverse), such as Shockwave, Springer, Galvatron, Astrotrain and Blitzwing; Better versions will inevitably get a fairly quick release in the future, IMO.