I agree, if one hasn’t taken steps preventing keys from being numericnote, use of assoc is to be preferred. The latter is much slower at runtime than (the “dictionary” application of) item of though, which may become an issue when a larger database is involved. Besides, using assoc is slightly less convenient. I recently wrote a simple block (lookup) implementing item of for dictionary applications and supporting numeric keys.
Note: a simple measure is adding a non-numeric prefix (such as: “$”) to each and every key.