Keep in mind that loupes are useful for subspecialties beyond oculoplastics. Scleral passes in strabismus and scleral buckle prodecures are much easier with them, though admittedly not absolutely necessary. Having tried every major brand of loupes, my opinion is that Designs for Vision are the best. Our optical shop shares this opinion, and they have the benefit of 30+ years of experience servicing the ophthalmologists, ENT, vascular surgeons, and plastics guys(among others) within the Texas medical center. My considerations, in decreasing order of importance, are: optics, comfort, durability(i.e. construction and materials), support for repairs, carrying case(may seem silly, but I plan to use these for 10+ years--have you noticed the lens cases of your senior residents lately?), and eye protection(less of an issue for eye cases, but nonetheless...). I did not like models that had flip-up lenses (more opportunity for wear and breakage). Likewise, when the telescope portion was not in-the-lens, I felt that it was too easy to shift one or both loupes out of my visual axis. Plus, I don't typically need to flip my loupes out of the way during an eye case. Having said that, one of my ENT friends has Keelers, and has been happy with them over 3 years.
As far as the process of acquiring them, the typical routes are through a retail channel (e.g. an optical shop) or direct from the company. In the latter method, they may send out a rep to measure you. The price is typically slightly better. The downside is that if there is a problem, YOU have to deal with them directly. Some of my co-residents have done this, and the process is a pain, to say the very least. My bias is to go through a retail channel.
Finally, keep in mind that some people negotiate loupes into a sort of 'signing bonus' when signing their first contract.
Just my humble opinion; feel free to ignore!