If you REALLY want to judge line, you need to look at the diameter of the lines. The American "lb test" rating is so off the wall that you can't compare line based on it. In essence, you can take a 40lb test line, put it in a box that says 30lb test, and sell it as the "world's strongest 30lb line". That's exactly what Berkley does with Big Game, as told to me years ago by a person in the industry.
If you look at Trilene for example, the same lb tests lines in XL and XT have different diameters, with XT being promoted as "stronger and more abrasion resistant". Well of course it is, it's the thicker line of the two.
A thick 20lb line will have more abrasion resistance than an ultra thin 50lb line will, as people who hate braided lines will rant about all the time when comparing mono to braid.
When I shop lines, I compare diameter to stated breaking strength. I am generally looking for the thinnest line I can find, in either mono or braid. Thin line means more capacity, it's easier to tie knots and manage overall, and it's less visible to the fish in any color. I don't shop for lines based on being abrasion resistant, because all lines are resistant enough for what I plan on using them for. If I need additional resistance, then I use a leader of thicker line.
All over the world, they label lines with diameter first then breaking strength. That way, say, you want to fish a light test line (for a record) for a fish that lives in or around thick cover, you can find a line that is more ideally suited for your requirements.
Line diameter measurement is also the only true way of knowing about how much line your reels will hold, unless you actually measure it. If you look on the reel, it will say LB test capacity on one side of the spool and usually either MM or hundreths of an inch on the the other side (a spinning reel spool). Baitcasters usually have them listed under each other. A reel that's rated for 200yds of 20lb line will hold more than that in a thin line, and less than that in a thicker line.
Here's an example. For Father's Day, my oldest son (10 years old and always looking out for me!) bought me a Shakespeare Alpha spinning reel. It's rated on the spool for 190yds of 20lb line. He bought a 225 yard spool of Zebco Outcast 20lb line for me too. I could tell that it was a thinner line compared to some 20lb lines, and the whole 225yds filled that reel perfectly.
Just for giggles, I had an old spool of Spiderwire Super Mono (hate that stuff) from last year that I spooled on before the Outcast. It was a 220yd spool, and there was 25yds left when I was done. Yes, I measured it, I'm goofy that way.
Conversions from mono to braid will also affect capacity. An example here would be a Shimano 4000 size spinning reel. Just because a reel holds 160yds of 12lb line, doesn't mean that it will hold 160yds of braid with a 12lb mono diameter. It will hold 145lbs of 50lb Power Pro, with is a similar diameter to most 12lb monos.
You said yourself that you could tell the 40lb Big Cat was thicker and stiffer than the 40lb Big Game, so, in theory, it should be a stronger and more abrasion resistant line.