Comparison: epoxy resin vs. glass
About a year ago, I created a epoxy resin based river table for my dining room involving a couple of live-edged oak panels joined by a river made from several hundred dollars worth of metallic blue colored epoxy resin.  My first attempt failed miserably for a variety of reasons.

I didn't adequately dry the fresh cut oak which meant that water lurked just under the wooden side of the epoxy/wood joint.  I also didn't seal the wood adequately before applying the resin so after the pour, the heat from the resin's hardening drew the water out of the wood and into the resin, making the resin cloudy and ugly.
I also poured too much resin in each layer and poured it on a early winter night when the temperature in my workshop suddenly dropped twenty degrees.  The sum of these temperature related missteps was that the resin cracked in several places, leaving jagged lightning-bolts throughout the &quot;river&quot; portion of the table.  Ultimately it shattered completely as it cooled.

My second attempt was significantly more successful, though I never did get around to putting legs on it.  With the oak properly dried and prepared and with much more patience during the resin pouring, I managed to produce a 3' x 8', mostly flat surface with a beautifully un-shattered river center stage.
This is where I finally get around to answering your question, &quot;how does resin compare to glass?&quot;.   The answer is, it depends.   For the vast majority of the pour, I used a comparatively cheap resin, one stage up from what is normally used to make fiberglass.  It's greatest attribute was that it was supposed to be foolproof.  My first attempt definitely proved that wrong but after I got the hang of it, it was pretty easy.  I left the project alone to cure for about a month and when I returned I found the surface hard but not as hard as glass.  I could definitely &quot;dent&quot; it by dropping metal objects on it and I left a few fingernail gouges in it as well.  It was about as hard as drywall and had a slightly oily feel, even after a month of curing in a cold garage.
So I called the shop where I had bought the original resin and described the state of things.  They happily sold me several gallons of another (more expensive) resin which they called a &quot;hard coat&quot;.  Sorry, I don't have any real product names.   I sanded the table everywhere to help with adhesion, then poured this new resin over both the previous resin and the oak, allowing it to pool over the entire surface which I had surrounded with a masking tape fence.  The new resin was clear but it made the wood look amazing.  It also brought the dull sanded surface of the old resin back to transparency with a gorgeous glossiness.  This surface cured clear, flat and hard.   Metal coins bounce off without leaving a mark.  Cat claws and fingernails fail miserably in any attempt to scratch it.  The edge is sharp and would be straight if I had thought to use something stronger than masking tape for the wall around the final pour.
That table top now holds a proud place in my gallery of unfinished craft projects.
I don't have any scientific instrumentation to measure the difference between this final surface and glass, but the &quot;hard coat&quot; resin will definitely stand up to years of normal indoor usage.