The Scarab should be a good solid boat depending on how it was cared for. Build quality on all 3 boats in that year range is probably relatively equal. Ride quality in the Scarab will probably higher than the others with the Fastech being comparable.
I have owned 3 others and currently own a Scarab. I have never had any issues other than very minor that would relate to build quality.
Have a survey done prior to purchase. If it checks out good and you take care of it after purchase, you should have no trouble with the boat itself for a long time.