Greg, I totally agree that level lines are ultimately the way to go in Tenkara for most circumstances… but especially when starting out or when casting dry flies with lots of wind resistance, they add a lot to accuracy in casting.
"Furled lines may be easier to cast, but harder to keep off the water…"
This confused me, because unless one is fishing lakes and intentionally throwing 20-30 or more feet of line, (which is really hard to do with level line, especially if there's any wind and if one is using a stiffer rod) there will never be any leader or line on the water… only tippet.
For example, if one's rod is, say, 13 feet long, and one were to use a 12 foot leader with 3 feet of tippet, one would have an almost perfect triangle between you, your rod/line/the water… the only thing that would ever be on the water is one's tippet, right?
If you have any line on the water in a river, I'd argue, IMHO, that you aren't taking any advantage of what the Tenkara style of fishing has to offer. I'm sure you know this already and I hope I don't sound silly spelling it out like that.
"1) makes strike detection more difficult,"
How does having line on the water make strike detection more difficult?
"2) are harder to clear of a wind or bad-cast tangle,"
In my experience they don't tangle in wind nearly as much as lighter lines do, and since they're made of furled lines, they do untie really easily unless you pulled really hard on a snag WHILE tangled.
"3) can spook the fish as they drift over"
DEFINITELY agree here, but more as you cast over since you shouldn't have any line on the water :)
"4) drip water which can spook fish."
True, although I've never had this issue since the line isn't usually wet or on the water.
"They aren't exactly cut to fit like a level line."
This is true, but you can order them in any size for $13-$20 each depending on your choices and source… I'd be happy to point you to a few sources if you're curious, I have bought them as short as 6' and as long as 12' since most of the rods I have are 13.5 feet and shorter. This makes them more expensive. But if you only have one fixed-length rod, you only need one furled leader.
"Nor can you add to them if you want another 3' for a particular situation."
You definitely can, by using some level line, just as you would with a western setup.
Best level lines I found were in Japan, they are way more visible than most of what we have here…. and we can't get those same ones easily here, but I am fully a proponent of using level lines.
Even though we may disagree on some of the specifics, likely because we fish Tenkara differently, I too think every Tenkara fisher should have level line in the bag when fishing.
I've never used a 4.5 so maybe those can throw dries and act a bit more like furled leaders.
Either way, both work, although usually for different fishing situations.
I tend to use the furled leaders on windier days and when fishing dries, to get the line to cut through the wind the way I need in order to cast, and in order for the line to "make up" for the difference in the wind resistance of fluffy dries.
Other days I reach for level line, and almost ALWAYS use it when fishing sub-surface, in case I do want to get a bit more sloppy with my form or change the length of line more easily.
Anyway, tight lines and I hope you're catching fish already! Our season just opened here in NY a few days ago.
(edited to clarify a bad sentence.)