A very important factor in your aircraft search is how many passengers you want the capability to fly. In the super-mid-size cabin class and larger, different configurations will impact the amount of passengers you are legally allowed to carry. The Bombardier Challenger 604 and 605, for example, have the option of having a conference group or a divan and two chairs. One option provides seating for 8 passengers in the cabin and the other 9. If you want 9 seats in your Challenger, then you will have to get the divan seating arrangement.
Another specific example is the Bombardier Global Express which can either have an aft cabin with two divans or an aft configuration with one divan and two chairs. The former seats 14 total in the cabin and the latter seats 12. The Gulfstream V and G550s have similar aft cabin options.
When you have set your mind on a certain configuration or a certain number of passengers, you could be significantly limiting the supply of potential aircraft to purchase. Some configurations like the Challenger 604/605 are about half and half on having the conference group or having the divan, so desiring one of these layouts or needing to seat the max number of passengers would not significantly impact your search. On others though, such as with the Global Express, only a few aircraft have the double divan configuration. If seating 14 passengers is very important to you, you will have to wait for one with the divans to come to market which could potentially be a long time.
Most of our clients rarely ever use the max capacity they think they will. We recommend taking a good look at how frequently you actually need that max capacity and tailor your search from there.
Knowing exactly what you want in your aircraft can be incredibly helpful, but at the same time, if a certain configuration or a certain passenger capacity is one of the most important factors to you, there will likely be ramifications of time or money that will need to be accounted for during your aircraft search. Tell your aircraft broker your specific needs and desires so you can be prepared with what supply is available to you and other possible options to best suit your needs.