The answer you're looking for has to do with time, and how you want to use the transposition. Neither line is necessarily better though it/or can keep your opponent off balance if they have not researched or studied the line.
Is the Neo-Catalan better than the traditional Catalan?
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5... d4 looks like a pain to deal with, but I suppose you do avoid Bb4+, which is nice...
Engine eval is equal between the two...
Considering neo-catalan is less common and will throw people off better I'd probably prefer it over the catalan, all other things seeming equal.
The point of the Neo/Catalan is you don't fight for the Central Pawns so much as you fight for Sqaures and piece placement. Most of the time. Pawns are targets for your opponents to attack so you gain better development and intuitive.
This is the Neo-Catalan
This is the traditional Catalan