I would guess that in the majority of cases the deciding factor would be the skill of the bonder. In the case of acrylic, having nice straight, even seams that make contact throughout the whole length (no jagged edges, gaps etc.). I would think glass with silicone would have slightly more margin for error as silicone could fill small gaps and provide added strength through edge fillets. I have never built a glass tank, but I have built an acrylic sump. I had a glass shop cut the acrylic to size, and they made the edges a little rough. It was a huge pain to get it together and sealed right. The uneven edge gave me tons of trouble. Tons of tanks are made of glass/silicone, so there doesn't seem to be a lack of strength with that route. If I was going to do it, I would go for acrylic due to the fact that I could cut it myself to ensure good seams.
