2mm vs 2.5mm

Welcome to the G!!

When I was relegated to hand cutting all the glass at our shop, the 2mm certainly cut easier, and, depending on the size of the sheet, broke easier. It also chipped and literally 'broke' or cracked easier. I've picked up a meticulously cut sheet of 2mm, trying to be very careful, and if it was a fairly large sheet, had the mere weight of the glass cause it to break.
The 2.5 or even the 3mm can be a bear to break cleanly unless you have your cutter clean and lubricated.
I used a hand cutter exclusively, because we didn't have a wall-mount cutter. I think most everybody else uses a wall-mount cutter, so my opinion may be a moot point.

Check the 'DIRECTORY' function at the top of the main page, and search for 'sanabria'. She was located in Charlotte, and was associated with Guardian Glass.
I prefer the wieght and "protection" of the 2.5 mm glass. However, many mouldings have a 3/8" rabbet. If it's the only design that works and you are putting in a double mat, sometimes the 2mm gives you just that extra room to comfortably put the points in. SO I have both around.
I prefer the 2.0 mm stuff, myself. Not only does it weigh 20% less than the 2.5 mm variety, but from my distributor, it is less expensive (not by 20% though) :(

Often the 2.0 mm glass does not come pre-washed, but I clean everything anyway, so that is not a big deal as far as I'm concerned.
Since the strength of a lite of flat glass relates
to its thickness, the thicker varieties will be
safer, as Charles' experience demonatrates.