1. Eyepieces and off axis aberrations:
Most cheaper eyepieces assume the light coming in is in parallel rays. When the f ratio is small, then this doesn't hold true as the angle of the cone of light is quite steep. This produces coma-like aberrations away from the center of the eyepiece and is worse with widefields. Televue eyepieces are able to correct for this defect down to f/4
On the other hand, the primary optical disadvantage of a newtonian telescope, Coma, is not corrected for except in a very few, special and out of production eyepieces. This too causes seagull shaped stars away from the center of view and worsens with decreasing f ratio. This optical aberration requires a coma corrector, such as the Baader MPCC, Astrotech Coma Corrector or the much vaunted Televue Paracorr. Merely sticking a TV eyepiece in would not correct for Coma.
On a personal level, I have a 14" f/4.7 newtonian in which I don't see the need for a Paracorr visually even when using my widest EP, a 31mm 82deg. When using a CCD though, the co,a will be very apparent.
Also, poor collimation will produce optical defects far worse than coma so the mechanical construction of the telescope in how well it holds its collimation and how easily adjustable it is to collimate is important.
Again, having said that, its not difficult and I get very good views after less than 10mins collimating my 14"
2. Focuser: Crayfords are not necessarily superior to R&P designs. What matters is the quality of the machining. A well made R&P will outperform a poorly or even average-ly made crayford as R&P, when well constructed, tend to bear loads better without slipping. I'm not saying they are a superior design therefore, but just to point out one design is not necessarily inferior to the other.
Hope it helps
Finally, if you intend to mate a camera, do ensure your choice of scope has sufficient infocus to allow you to do so and come to focus!
Hope it helps
