Terms like "tip flex"(an orvis exclusive) or "traditional spey-action"(a Sage invention) are really just marketing blurbs to easily describe something that is not so easy to describe. Powell catagorizes their new rod only as "fast". Abel's reference to the casting character of their rods is "sensitive tip". These are not very descriptive terms. They are kind of subjective in fact. I think that the Abel SW. rods are powerful, but more brutish than sensitive."What the hell does that mean!"
Taper descriptions are a little better. "Progressive" vs. "Compound" vs. "Parabolic", but even those easily defined categories don't tell how a rod will respond to a given line weight. Some rods feel under lined, or need to carry a lot of line out to feel properly loaded(to me). Others seem to collapse when pushed too hard. Ever cast someone's favorite rod, and say, "huh?".
Juro's point about line speed is good, but we have all seen people who can break the sound barrier with a "slow" action rod.
Its funny, because in their catalog, Sage doesn't even bother to describe the action of their RPLXi. I suppose that's a good thing because Juro's and my 3 Piece 9 foot nine weight RPLXis have noticeably different actions. We both love 'em. Go figure. Personally, I like a compound taper rod with a soft tip and a stiff butt for my floating and intermediate lines, and a progressive taper with a heavy tip and a stiff butt for shooting heads and teeny lines. I think that the manufacturers call both rods "fast". Reminds me of the guy in front of me at Starbucks this morning,"I'll have a Grande decaf mocha frapachino with three shots of espresso and soy milk."
One cast can change your day...maybe your life.