Will the SW be that much cheaper when you throw in the flattener?
BTW, I noticed a review here:
http://www.cloudynights.com/topic/38...d-80mm-f75-ed/ that mentions the author's previous Williams scope...
Personally I think if you are going for a "lifetime" scope then you should get the best you can afford. Williams scopes are very well made, and their service is very good (I have dealt direct with them in the past and they bent over backwards to help). This particular one will give you a wider field than the SW and as a triplet it will probably be better colour corrected and therefore give sharper images for astro photography.
All the best,
Dean