As someone who has read several applicant's LOR (both for residency application and for private pratice MD job applications), I can say that very few letters jump out at me. Most letters say the same thing; unless of course, they say sometime lukewarm or negative about you (such as being lazy, inconsiderate, etc).
Given the above point, I am often more interested in the applicant if the LOR I'm reading is from some bigwig, or someone I know personally. I may not know all the bigwigs, but I'm more impressed when the the letterhead is from department Chair, professor emertisus, or etc. Similarly, if the LOR letter is from a buddy of mine, then I'll perk up in reading what my buddy has to say about the applicant.
You can't control who will read your letters, nor exactly what the letter will say; but you can try to get a letter from someone more involved in the academic circles of your speciality choice.
