I bought a Propper head mounted Small-Pupil BIO way back in the mid-1990's when I was a student and it still works and it is my BIO of choice to this day. The only problem has been with some of the chargers, which I had damaged by dropping on the floor, or just wore out. The electrical cord from the BIO to the charger went bad after 12 yrs in practice and they replaced it. No problem with the BIO itself. The company was bought by Heine and they have a similar model today. I may have had to change the bulb once - can't remember.
The head mount is so awesome that you can see ora on most patients without dilation, with training and experience, of course.
Patients like the scope because it has a yellow comfort filter and adjustable rheostat.
I also have a backup Heine Spectacle mount BIO and I bought the cheaper version with a diffuser and I don't like it as much. I like the version that provides a crisp circle of light for the view. The spectacle mount is so heavy that it hurts my nose.
I don't like the Welch-allyn Indirects or Directs because I can't see as well with them. You can't do a decent undilated peripheral fundus exam with the WA indirects, and you can't even see very well with them undilated and direct. They're just not as good. In short, they S*CK!
However, that said, Welch Allyn makes a far superior retinoscope than Heine or any other companies.I have a WA retinoscope. It is awesome.
So, that's advice from an OD who's been practicing for over 15 years.
The increased fee for the Heine BIO is worth it because if you work commercial optometry you WILL be required to know how to do an undilated fundus exam and for legal reason's you WILL need to be proficient and skilled enough to see ora with it in most patients. You can't do that with the other scopes, in my experience. (You have to work FAST in commercial and the Heine BIO will allow you to do it).
The other option is Slit lamp BIO combined 120D lens. The view with that lens is superior to Optomap! I actually do slit-lamp BIO more often than headmounted. Also, I have the patient turn their eyes in all quadrants with the 120D and you can see ora in most patients. I combine it with 78D lens for a good view of the macula.
The 120D lens I have is called Ultraview SP. It's hard to find anymore though. Only drawback is that you have to be close to the patient's eye to get a full-field view. It requires daily cleaning. Other than that, it is awesome!