Would vs. Could
Dear Grammer Cop,
When do you use would or could in a sentence?
If you feel that any of your patients would/could benefit from chiropractic care please keep our office in mind.
In this context, "would" is definite, but conditional--it will happen if certain conditions are met. "Could" is a possibility--it may or may not come to be.
Think of it this way:
Would's root word is "will"
Could's root word is "can" - you can substitute it with "might" or "maybe."
Here are some examples (assume the speaker isn't lying!:
"I could run a mile in five minutes, but I don't want to right now."
The speaker can actually run the mile, but it's only a possibility.
"I would run a mile in five minutes, if my leg weren't broken."
The speaker can actually run the mile, but only if the leg weren't broken.
In your example, "would" might imply a guarantee, though, and that's probably not something you'd want to put in writing.
Consider this rewrite:
"If you feel that any of your patients would definitely benefit from chiropractic care, please keep our office in mind."
"If you feel that any of your patients could possibly benefit from chiropractic care, please keep our office in mind."
The comma is needed to offset the introductory phrase :-)
There are other uses and forms of "would", like in the subjunctive mood when being polite, but they really don't apply in this case.