Like most aerial work the environment over which you work is a significant factor in choice of helicopter.
Twins over cites, big engined singles when hot and high ect.
Rear fenstroms if noise is a significant issue (ie shooting animals or sensitive, populated areas)
Also a factor is the $$ cost of transit between a local aircraft and a more ideal craft that is hours away.
Availability of floats should be considered if you do marine or coastal work.
4 POB in a R44 for low level aerial photography on a hot day has less safety of a margin than 2 POB.
Working from the rear seat is preferable to eliminate the rare chance of camera equipment fouling controls.
A sliding door is preferable to removing the door.
There are after-market kits that install a slide down window in most helicopters so a sliding door can remain closed or enabling the use of a hinged door. Operators often neglect to mention this on their websites.
A compact helicopter with a high degree of manoeuvrability is always an advantage, but not essential for many assignments.
Large or slippery shaped helicopters can be more difficult to slow down, but tend to have ample power once they are in a hover.
Skill and experience of pilots is a factor, up to a point. Very low hour pilots, lets say under 1000 hours, should be avoided for complex jobs with high degree of pressure or low level work in a helicopter flown with little power margin.
Since helicopters are charged by time in the air, comparing maximum cruise is prudent especially since cruise speed with doors off is usually lower than door closed.
Mickjoebill