You might find a chair that more specifically meets your needs, even one that can be more aggressively customized for you. Since smaller producers don't have huge production schedules, they may be able to deliver your chair faster than a large company. You might be able to find a better price. One issue you will want to consider before deciding to purchase from a small producer is how important the look of your chair is to you. Wheelchairs designed by the smaller companies often tend to look like they were designed by an engineer, whose concerns are wholly functional, and whose training does not include aesthetics.
Engineers are interested in the operation of the chair, and the ease of manufacturing it.
This is not universally true of small producers, but is more the rule than the exception. If you are the personality type who is practical and unconcerned with flash or looking hip, a chair that looks like it was designed by an engineer is no problem for you. In fact, it might be the better chair. However, if you are concerned with appearance, be sure to ask about this. You will also want to ask about the ease of finding service and getting parts for a chair made by a small manufacturer.