As mhurley say, Some time back Clarity Plus was putting a "cheapo" product in the market with thinner than required acrylic and had lots of complains and quality issues. (I know, I been there) Apparently after they were acquired a year or two back they seem to have been putting a better product. In any case, I got my frag tank from Tenecor and I can say quality and strength way surpasses the one of Clarity Plus which I know I will need to replace or one of this days I will have a tragedy around.
So if they are the same dimensions first thing to check is for pane and tops thickness and for the quality of the seems with no crazing nor bubbles. If by then they still compare then look for less scratches.