Having played both the remaster and the original, I can safely say that the original plays better.

From the needless changes to the levels, extra collectibles, extra crates (they are literally everywhere) to actually bad things. For example, when you command your comrade to go grab a roman, it works pretty much flawlessly in the original, but in the remaster, Obelix always runs up to the roman but stops just before him and does not grab him. The extra crates are also often carelessly placed in the way, so much so that you often have to go back and destroy some of them because the old pathfinding can't handle all the new crates.

Lions and tall legionaries were nerfed and their attacks have been slowed down so that they are mostly harmless. Speed on slides has been greatly reduced, making the helmet collecting challenges trivially easy.

Not to mention new graphical bugs (like lines between textures) to screwed up audio balancing (the shop for example is insanely loud in the remaster).

Even though you can swap to the retro mode, you can't do so on the map or in the shop and the music does not loop properly in the retro mode (it loops without issues in the original).

I was initially playing through the remaster but after looking into all the issues and changes in it, I just replayed the original XXL.