I was thinking about this yesterday-I needed some tippet and a store I stopped out was out of the size I wanted. Thought about just buying some Berkley mono...what REALLY is the difference!? I assume it's thickness, but there has to be SOMETHING that is comparable.
First off with leaders & tippets, diameter is everything. Breaking strength is overrated if you know how to play fish as evidenced by IGFA records on 2lb test...
When it comes to using fishing line as lieader material or tippet as already has been mentioned; the diameter of fishing line for a given breaking strength versus the same breaking strength of purpose manufactured leader/tippet material will ALWAYS be fatter...
So, if you want to substitute fishing line for leader material and want the same "behavior..."
DON'T choose a fishing line that matches the pound test of your leader material. Choose a fishing line with a stated diameter as close to the DIAMETER that matches your size & brand of leader material...
Then put a micrometer to both so you know if you are comparing apples to apples.
😉
If you want consistency in diameter, buy Japanese fishing line that is rated in their "Gou" (pronounced "go") system that is based solely on diameter, NOT breaking strength.
Japanese Domestic Market (JDM) lines are WAY more consistent (and honest) in regards to diameter than their US counterparts. Companies that are members of the JAFTMA (Japan Fishing Tackle Manufacturers Association) will STRICTLY adhere to the standards so if you buy a 1 Gou line, it WILL be 0.165 mm or .0065" in diameter.
Even if the Japanese fishing line doesn't have the Gou number on it, you can generally trust the diameter because pound test has nothng to do with the marketing of the line.
It is becuse of this consistancy and the quality of the product that for my conventional fishing, I switched from my long, long, long, long time favorite Berkley fishing lines to Sunline, Varivas and other other JDM fishing lines.