argh
nobody knows eh?
it boils down to about $100
Top Fin 120g from Petsmart = $289 = 306.34 with tax
All Glass 120g from Petco = $379 = 401.74 with tax
to me almost $100 is a lot of money ... long hours spent at a boring job

... so I'm leaning towrd the top fin at this point... besides I would rather have the $100 to spend to avoid cutting corners on something like lighting, filtration and livestock.
Although I'm not a big gambler, I feel the odds are about even on the chance that either tank could leak or rupture.
I have never had a tank rupture before, but I have had them leak, mostly due to my own carelessness by handling them from their top support band, rather than the bottom.
this new tank will hopefully suffer no such abuse, as it weights about 200 lbs and will be carried by at least two people.
from what I can see, the tanks appear to be identical in assembly - butt jointed walls, full base bottom, single piece molded top support and center span.
I know it's generally bad to cut certain corners, and this is why I'm buying a premade tank instead of trying to make one myself. for the most part I have more faith in modern industrial assembly technics than I do in my own when it comes to something like this.