Rangefinders have certain advantages with certain lenses. One advantage is that every lens you use will focus the exact same way. Doesn't matter if the lens is wide or tele, or has a narrow maximum aperture or not.
Wide angle lenses are much easier to focus on a rangefinder. I can't speak to many other rangefinder systems, but Leica's is great from 21mm to about 75mm. Filters are another advantage - they don't darken the viewfinder like on a SLR.
The hardest things about rangefinder use is the need to develop "pre-visualization" skills, and using longer lenses. The frame lines get tiny at 90mm, and 135 is pretty much the maximum. I can focus a 135mm on my M3 (with its higher magnification finder) pretty accurately, if I stop down a bit. On a standard .72 or .68 finder, 90mm becomes challenging. My eyes are getting old - you may have no problem with a 90...
Once you get to know a few of your lenses, and how they render at different apertures, you can visualize how the final image will probably look. Sometime, the results will surprise you, too.
SLRs are more accurate with framing (if you've got a camera with a 100% finder), and much better at longer focal lengths.