Over 200gallons I prefer Acrylic, yes it can scratch, but if cared for IMO it's better.
I believe it's 17 times(can't remember were I learned that) stronger than glass and 2-3 times clearer when in thick sheets. It is much lighter than glass. I find it allows many more plumbing options for hidden plumbing, without compromising as much strength as glass. A major plus is that tank drilling can actually be done without taking the whole tank down(obviously above water lines).
I like shaped or curved tanks and acrylic is far more accommodating than glass. I do have to say Oceanics bowfront line is very nice for smaller tanks.
As to scratching, yes they can scratch. They can also be buffed and repaired to almost new. As in glass there are different grades to acrylic like glass. I've even found noticeable differences in quality between manufacturers. Much of what we see prebuilt in stores is of the lowest grade, often extruded not cast (cast is much better).
The range in fabrication quality is HUGE. Most of what people get is solvent glue fabricated. This produces weaker seams although stronger than glass they often are opaque and or have bubbles. Liquid acrylic is used for clearer seams which are stronger. This method is more labour intensive and costly. seams can also be polished before gluing to give perfectly clear seams. This can add allot of cost but produces a very nice looking tank.
As to scratching, proper care goes a very long way, I have some acrylic tanks 7+ years with almost zero scratches. I use Quickwipes from Coralife. They are like felt and wash out easily. For deeper tanks I use two proper acrylic brushes. One for the gravel line, and the other for the main viewing areas. I don't use magnets. They are easier but they can easily pick up debris and "drag" it across the tanks scratching it. On the outside I either use water or acrylic spray, never Windex! It degrades the acrylic and can reduce clarity over time(plus if it gets into the tank via spray or my hand, it's toxic to fish).
A major benefit to all you reefers, when you have a rock avalanche, the chance of acrylic shattering is drastically less than glass. I've noticed in different areas of North America people prefer glass or acrylic. In California a earthquake zone Acrylic is far preferred. It is also what most Public aquarium viewing panes use.
Unfortunately Acrylic is almost always more expensive
