I have owned the 2.55 Mini, 225, 226. The Mini is the only one currently in my collection, as I like smaller bags, and I sold my vintage 225 to fund another I still like the 225 and would consider adding it back into my collection, preloved because retail is highway robbery.
If you prefer smaller bags and the Mini meets your needs, then I would say you don’t need the 225. The 225 is a nice size, just a little bigger than the Mini, elongated so it can fit longer objects (or two objects side by side) should you need it to. I prefer smaller bags, so having both wouldn’t bother me. I would have a use and purpose for both.
A note on the name of this style and sizes: the style was named 2.55, because Coco Chanel created it in February 1955. Chanel fans call the sizes 224/Mini (224 has a double flap, Mini does not), 225, 226, and 227. There is no need to put a period between numbers for the size. Online, I think the sizing is Mini, (225 has no size in its title, but I think FAs would call it Small), Large, and Maxi.
If you prefer smaller bags and the Mini meets your needs, then I would say you don’t need the 225. The 225 is a nice size, just a little bigger than the Mini, elongated so it can fit longer objects (or two objects side by side) should you need it to. I prefer smaller bags, so having both wouldn’t bother me. I would have a use and purpose for both.
A note on the name of this style and sizes: the style was named 2.55, because Coco Chanel created it in February 1955. Chanel fans call the sizes 224/Mini (224 has a double flap, Mini does not), 225, 226, and 227. There is no need to put a period between numbers for the size. Online, I think the sizing is Mini, (225 has no size in its title, but I think FAs would call it Small), Large, and Maxi.