Steven, there are a lot of different model Bessa's. they began in the 1920's and were Voigtlanders first 'self erecting' roll film camera, over the years naturally they made changes, so their appearance and features changed somewhat.
the Bessa 66 (66 stands for 6x6 format.) they were also called baby bessa, because previous bessa's were all 6x9 format. the baby bessa (or Bessa 66) is most often found in two different variants, the base model with pop up frame finder, Prontor II shutter and Voigtar lens (their entry level lens). The other model has the optical finder and came with a wider choice of lenses, Voigtar, Scopar or Heliar, it also had the better Compur Rapid shutter..It came in three versions, basically it was the film counter that was different. by the last model the film counter was fully auto.
As you noticed the shutter trigger is on the front door/bed, just the same as the big Bessa's, some people dont like the shutter there but others do, i find it very easy to use depending on what year and model Bessa it is on, the early ones arnt quite as smooth as the late model Bessa's, there is a difference in the build and quality of the components in the base model Bessa's (6x9)trigger compared to the rangefinder model Bessa
the shutter on the Bessa 66 with the auto film counter system is not the best of the Bessa's (it is probably the worst). with this camera the shutter as it depressed also has to operate the system for the film counter which makes the camera trigger not as smooth and more prone to camera shake.
the Perkeo's come in 3 different models, the Perkeo I is most often found with Color Vaskar lens (the C/Vaskar replaced the Voigtar) but occasionaly found with C/Scopar. the perkeo II (much more common with c/scopar and 1/500 shutter now) now has the film counter (like perkeo I) and double exposure prevention. the perkeo 3 (E) is scarce but fwiw it has a built in rangefinder
if you had to choose between Perkeo I or II and Bessa 66, then the Perkeo is much nicer (more so with c/Scopar and synchro compur shutter--very sweet camera then) to use and gives better results. Only reason i would choose the Bessa 66 is if i was wanting the Heliar lens (not available on perkeo) or liked the built in yellow filters they have (for b&w), otherwise the Perkeo is much smoother, smaller, more functional and better quality design and results.
the Bessa I is Voigtlander's post war 6x9 camera, made at the time as the Perkeo and with simular features and lens options but otherwise not to be confused with each other or the Bessa 66