Choosing what RC FPV aircraft to use for your first attempts at FPV should be a very straight forward decision. It should be a model you are very comfortable flying, it should be a slow & stable flyer, and it should of course be reliable.
Secondary considerations are based largely on how and where you intend to fly FPV style. For example, are you planning on fairly long distance flying or closer in? If long distance (well out of visual range) is something you want to eventually do, chances of losing your aircraft increase; so it better either be fairly inexpensive/expendable, or have a very good return to home autopilot system (not many are good).
Likewise if you fly over houses or other occupied areas (which is usually illegal so you should never be doing it anyways), you best choose a light foam airplane to keep liability at bay if you lose control of the aircraft or it has a mechanical/electrical failure and falls out of the sky onto the unsuspecting terrestrial beings below.
Just the thought of flying a big 700 or 800 size RC helicopter by first person view out of visual range and over occupied areas scares the living daylights out of me (it should scare you too).
On the other
hand, if you live in a rural area and will only be flying over nice big empty
fields and forest (such is my situation), having a large & potentially
deadly RC model falling from the sky is a little less risky if you don't mind
the possibility of losing it for good. Plan your flight & use common sense!
Another secondary FPV aircraft consideration is the view out of the on-board camera. For example, if you have a conventional RC airplane with a prop up front, your camera view is likely going to include a fairly big area of spinning propeller. Some people really like that and again it is very much what you would see out the cockpit of a full size single engine airplane. If you don't want to see a propeller, then other aircraft to consider are pusher prop types, wing mounted motors, quad/multi rotors, and of course helicopters.
Personally (and this is being an RC helicopter pilot first and foremost), I don't ever see myself flying a collective pitch heli by first person view. There are just too many complexities and even dangers with CP heli flight that would make it very difficult and overly demanding taking much of the FPV fun out of it (at least for me). Remember, CP helicopters are inherently unstable and you want a stable aircraft for your first FPV experiences. One caveat to this is if you use an electronic flybarless system with horizontal or autopilot stabilization modes such as the DJI Naza H, Skookum 720, or Bavarian Demon 3SX.
these will keep your heli from pitching or rolling past a certain degree making
your unstable CP helicopter as stable and predictable as a micro coaxial or multi rotor. If
you want return to home autopilot, get a FBL system that also supports GPS and
return to home functions. The DJI Naza-H is a great system for CP FPV aircraft, and if I ever do decide to try out FPV on one of my collective pitch helis (not that I ever will), the Naza-H with the GPS module is what I would personally use.
This all adds yet more complexity, cost, and possible
failure points. Remember, keep it simple to start; a CP heli is not simple no
matter how you slice it with or without an autopilot system.
Size of FPV aircraft is also an important consideration. FPV
equipment (the camera, video transmitter, antenna, and perhaps the OSD (on
screen display) take up space and combined, weigh a fair amount meaning you are
not going to be flying FPV with a micro sized heli, quad, or airplane. Spacing
your video transmitter/antenna as far away from your receiver and GPS antennas
is also an important consideration. The more separation, the better!
Flight time is another consideration. If you only fly close in, you won't need as long a flight duration as if you are going on longer distance flights (another reason why CP helicopters are not a good first FPV choice). My advice is to stick with a nice stable slow(er) foam plane for you "plankers" or an easy to fly multi-rotor for us "rotor-heads" as your first FPV aircraft.
So what do I fly for my first intro into FPV and why? As you may know from my FPV RC Introduction page, I decided on a DJI F550 Hex-rotor. I chose this aircraft for many reasons that were important to me and most likely very different from what you will want; but again, these are some of the reasons you should also be considering when choosing a specific FPV aircraft...