The 550 has wider ankle and middle areas.
For normal or narrow width feet: go down half a size from your true size. (ie: I am a true size 9.5 with regular width feet, so I buy my 550s in a size 9).
For wider feet: go true to size. (ie: I am a true size 9.5 with wide width feet, so I buy my 550s in a size 9.5).
The 550 does NOT come in wider or narrower widths.
Comfort Factor Ratings:
Cushioning (Softness): 2/10
Stability (Firmness): 9/10
Cushioning to Stability Ratio: 2:9
Midsole Shape (Foot support): 2/10
Since the 550 is a retro basketball shoe from the 80's, it is NOT a comfortable shoe.
The retro models DO come with an OrthoLite foam insole with some added cushioning and arch support, but that's about it in terms of any comfort technology. The 550 has a hard rubber midsole with a hard rubber outsole and that's it. It may have been comfy enough for basketball in the 80's, but it's 2022 now!