If your program doesn't pay for loupes, you might want to consider what I did at my program. We called the local salespeople for the 3 major manufacturers of loupes (Designs for Visions, Surgical Acuity, and one other one who I am blanking on at the moment) and had them come in for a head to head comparison one evening in the house officers' area WITH food. I organized the residents from Gen Surg, ENT, Ortho (hand), Plastics, Urology and anyone else interested (a few fellows and attendings that were looking for loupe replacements or upgrades).
We had them stay for about 2 hours so people could come and try on all the various brands one right after the other and make their own decisions. We also made the sales people offer a flat price that was a discount off the resident price (average ~10% off), no matter how many we, as a group bought, and allow our residents to access that price for a time period after that day in case they missed it.
Of the people that tried all 3, I'd say about 2/3 bought Surgical Acuity (AKA Orascoptic) 2.5X loupes which were the equivalent of DFV 2.5X extended field loupes, because they were cheaper and many felt that they liked the optics better (rounder field compared to the Extended field, and bigger field compared to the 2.5X standards). The other 1/3 mostly bought DFV 2.5X and a few buying 3.5X of various brands (mostly plastics residents)