Some updated opinions on this topic:
About the strength thing...unless it's extraordinary circumstances I don't think the average person is going to just 'bust' a glass tank unless they drop a 5 or 10 gallon one on a concrete floor or live in an earthquake zone. And tempered glass is available. It's not like glass is 'weak'. This is ridiculously overstated. Unless a 600 gallon falls off a pallet or is crushed in a warehouse, how often does that happen??? The worst you generally get is leaky silicone seals.
Regular glass and acrylic both can be drilled, obviously.
The clarity argument is a wash. Yes, acrylic is extremely clear but so is iron free starfire glass. And guess what? The slight green tint in regular glass all but disappears when the tank is full of water....light rays and color bend differently in water vs air. My 225 has starfire on the front with regular on the sides and I'm telling you there's no perceptible difference when filled. You see the difference when empty just barely...helluva genius marketing ploy! Like bottled water. I saw a website that had glass samples showing you the green tint edge vs clear edge pieces to convince you, GET THE CLEAR EDGE. Except you view through the pane, not the edges. The hype is real.
Substrate and decor affects glass clarity more than tint! It's not like you can't see the fish. More dated thinking.
Acrylic is more versatile with weird shapes. Best for commercial use due to fabrication limitations of glass with weight. But we're talkin' ginormous here. And weird shapes cost more for the average consumer! Sky high expense.
I should mention curved glass tanks are available but COST BIG BUXS $$$$$$ . And only certain companies make them. Fabrication cost a killer.
Acrylic has an obvious edge in weight but guess what? Once you get past say 300 gallons it ain't as much as you think. 1" glass and 1 1/2" acrylic are pretty comparable. So when people just say it's "light" like a 5 year old can haul a 12 footer, they're crazy. Lighter is more accurate. But it's gonna run about 70%-80% weight of glass at that point. Remember, bigger is thicker, so it's all about ratio when you go big. I'm not sure at what size the mass of acrylic catches up with the density of glass weight wise.
240 gallons and less with acrylic, you're gold with the weight.
Needless to say glass weighs a fricken ton, even at relatively small sizes (~100 gal up). 5/8" inch and up is where the weight explodes geometrically. However you have full open access up top without having to thicken the walls. BUT...
there is an exception! Rimless needs thicker, so now even a smaller glass tank weighs like concrete plus you can only handle it at the bottom!
but wait...GlassCages makes rimless acrylic tanks that look like regular framed glass tanks! But they need even thicker walls to prevent bowing with no cross brace. So we're back where we started with larger tanks.
The dreaded cross brace, a necessary evil of acrylic tanks. Over 125 ish, the openings are large enough for most deco and filtration. But you're still limited. I could never run 3 acl 100s with acrylic cutouts. On smaller tanks the cuts are a nuisance with cleaning under the edges and brace. Also acrylic will deform over time at the top! I read people whining about this a lot. Whether high or low quality, those braces will bulge and warp over time. It's the nature of plastics, not a flaw. In fact I guarantee it will happen around 6 months especially if your light fixture is near the top. So get over that...it doesn't hurt anything. A trick I find works is getting glass pieces cut to go over the openings. The acrylic lids will curl like potato chips every time.
Acrylic regulates temps better than glass. But don't be fooled by the dated thinking. Larger tanks don't fluctuate much regardless if its glass or acrylic. Plus, heat generated by pumps and equipment offset loss in smaller tanks. Evaporation is minimized with acrylic with covers. But that's true of glass too. So evaporation is a wash.
I haven't found scratching on acrylic to be a major problem.
Acrylic is ridiculously expensive, and the smaller tanks (50 and less) are disproportionately expensive even when compared to big acrylic tanks. Why I don't know. A 40 gallon 'kit' can be almost 700 bucks! It's insane.
I have both. So here's what I would do:
5-50 gal. Either acrylic or glass but understand the acrylic is gonna be 3-6x the price at this size.
65-500 acrylic for lesser weight. Glass for centuries and price if you have a crane and descendants into fish.
600-up acrylic or recessed concrete pool. Glass weight problematic and fabrication cost becomes an issue. Acrylic as an only option becomes insanely expensive for most. Lexan out of reach unless you're a millionaire.
Clarity a wash
Evaporation a wash
Temp control depends on size and setup
Acrylic will deform at top
Glass may leak at seams with age
So at the end of the day it depends on money, setup and what you want.
