So as we can see from these posts, each system has its advantages and disadvantages.
For work using deep-colored lens filters, including true infrared filters, it's hard to beat a rangefinder. Focusing and composing through a red or green filter isn't always easy, and focusing through an opaque filter is impossible, especially for the autofocus cameras.
If I was doing closeups, I would want to use an SLR. Same goes for those shots that require very precise framing, and then I would want a viewfinder with 95% or greater coverage.
For unobtrusive shooting, I would use a rangefinder and one with a quiet shutter, which probably would be either a Leica, a Retina IIIS, the Zeiss Ikon or a prewar or postwar (black dial) Contax. Maybe a TLR, depending on whether a single lens would be sufficient, would work too.
If I was shooting a sports event, I'd probably want a motor-driven SLR and might add auto-focus to the list.
With film cameras being a huge bargain, you can own more than one camera system and then choose the camera to fit the situation. Use the right tool for the job. This doesn't mean that you can't use a TLR or rangefinder with auxiliary lenses for closeup work, or you can't shoot infrared with an SLR. It just means that some cameras excel at certain tasks and come up short in others.