Due to my employers sometimes supplying photographic equipment, I have been able to use Nikon, Canon, Pentax, and Olympus cameras at various times for railroad photography. Each of these companies have produced camera models over the years which have been well suited for the task.
My favorites however are the Pentax MX and LX. My personal reasons for this preference are:
(1) They are both well made and very durable cameras which accept a wide variety of "K" mount lenses and can be used with 5 FPS motor drives, which share the same battery pack. (2) They both have mechanical shutter mechanisms (mechanical backup system for the HIGH shutter speeds in the LX) so you are not dead if your batteries go dead. (3) They both have horizontal travel focal plane shutters which are better suited to stopping high speed action than vertical traveling shutters. (4) They both have all the desirable features for railfan photography without being too large or heavy. (5) The MX with Pentax 40mm lens fits easily in my side pocket, and has been carried to a lot of very risky places including the mast platforms on Navy ships.
I prioritize my use of the MX and LX in the reverse of the preference of most photographers. I use the less expensive MX as my primary camera, due to its smaller size and lighter weight. I use the more expensive LX as the backup camera, when I need the special interchangeable viewfinder features that it offers. I also use the LX on a copy stand as a copy camera.
I have a digital camera (I will not advertise the brand) but usually use it only in situations where I have to transmit images by e-mail attachments. My primary interest is in color slide photography due to image quality, publication requirements, and preserved value of the photographic image. When an image can be randomly reproduced with virtually no loss of quality, as is the case with digital, it tends to have a very low value. With slides there is one original (unless you motor drive multiple shots of the same view), and any duplicate made from that slide is going to be of slightly lesser quality, which helps maintain the exclusivity and value of the originals.