I fall somewhere in between.
Pretty much everything is dust, bugs, moisture in the air or traceable to natural causes. Out of our investigations we've only gotten one orb anomally that I can think of right now that held some consideration. It had a measurable energy field that was about 2-3 ft in diameter in the middle of a hall at a 'high activity' location. A photo was taken of the location that we estimated to be the center of the energy mass, and there was an orb. We don't necessarily consider is a spirit, but more of a verified energy manifestation. Oh wait, there was one more incidence with an orb of interest. It appeared in 4 photos taken from completely different angles and light sources. We did get an EVP at the same location as the orb, but we've no proof that the two manifestations are connected. OK, as I write this I can think of one or two more that are of interest.
So, do I 'believe' in them? It depends on what you mean by 'believe'. I believe they exist, but at this point I don't believe they are manifestations of spirits (but I used to, heh). I do believe that they are (naturally) occurring energy manifestations. It is possible they have something to do with spirits- but not necessarily that they are spirits. I do suspect that there are some locations that promote paranormal activity because of available energy to draw from whether through being built over certain types of stone/ waterways/salt or electrical leakage. In that manner, it could be that these are also fertile areas for pockets of energy.
Who knows, it's still all guess work. For all we know they could be ghost farts! (hehehe!)
We don't even bother notating when we see orbs anymore unless they are accompanied by other data or have a unique quality to their manifestation.