dimensions

I will be getting a custom built aquarium for my Jardini once it outgrows my 6ftLx1.5ftWx2ftH. I am currently trying to choose between a 6ftLx3ftWx2ftH and a 7ftLX2.5ftWX2ftH. Which of these two would be better?

What id like to talk about is glass the types and thickness also how its used ... i understand why the bottom panel is much thicker then the front and sides but i have read that the sides must be thicker then the front also that it doesnt matter the highth of the tank ... also im wondering how...