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I like the Telrad for the graduated 'circles' that help with charts. But too big and cumbersome for me.
I like the dinkie little RSF. I have TWO. One sits on my 8" f/4 dob. The other on top of my BIG 3" finder of my 17.5" dob. The 8" is a rich field scope, so the accuracy of the single dot RSF is just fine.
Hickny has a Telrad & a 3" finder together on his 13.1"!
Hickny & I find that a red dot/Telrad are great as "gross" finders, yet the light gathering of an optical finder is a great help with fine tuning, or when the target is just not easily locatable.
If your scope already has an optical finder, I suggest just a single dot finder is a fine addition. Most times the RSF is sufficient. Yet, the optical finder gives me a little more 'guts'.
As an example, from my home, to find the Tarantula nebula last night, with my light poluted skies just using just the Telrad on Hickny's scope or the RSF on mine would have been a very, very difficult task. The optical finder had enough "beef" to actually show the Tarantula, and make locating it in the scope a piece of cake. The optical finder doesn't need to be like my overkill 3"er. A 30mm would have done just a good a job. Even if I can't see the object, the finder will show sufficent surrounding stars to assist with star hopping to the target.
The pics below show the RSF & 3" finder arrangement (I still need to take a photo of my completed 17.5" scope fully decked out with all its bells & whistles).
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