Hi Les,
I don't have any experience with the Starsplitter E/P's, but I have used the "Ultra" series (Siebert's top of line e/p's) + the Telecentric Barlow (again the top of line) for nearly 5 years. Great edge to edge sharpness and a great flat field and all this in 12" F5 Lightbridge.
Though they are plain in appearance, they are at their best where it counts.....Observing!!
Would I buy them again, if I had my time over?......YEP!!
My two cents....