I Wanted to see how the Spira stack up compared to other thrown secondary weapons, and I fugured other people might want to as well. I amy have left out some critical bit of information so take everything here with a grain of salt.
Stats of each, in case you want to compare them yourself (I didn't include Mk1 Kunai because they are just weaker kunai). B is base (total combined) damage per hit (DPH), AS is attack speed, IPS is Impact Puncture and slash damages respectavly (Seperated by commas) and DPS is Damage per second (obviously):
Spira: B:55 AS:2.5 IPS: 5.5, 33, 16.5 DPS:137.5
HikouP: B:32 AS:5.8 IPS: 3.2, 27.2,1.6 DPS:185.6
Kunai: B:45 AS:3.3 IPS: 4.5, 33.8,6.7 DPS:148.5
Dispair: B:55 AS:3.3 IPS: 2.75,44.0,8.25 DPS:181.5
Hikou: B:25 AS:6.7 IPS: 2.5, 15.0,7.5 DPS:167.5
Comparison, what each has most and least of (anywhere where something has the best ofsomethin is in bold:
Spira: Ties Dispair for top DPH; Lowest attack speed; greatest impact and slash; lowest DPS
HikouP: Top DPS; least slash
Kunai: Nothing, no highest or lowest of anything.
Dispair: Ties spira for top DPH; most puncture
Hikou: Lowest DPH; Highest attack speed; least impact and puncture
So, right off the bat, you see the Kunai is pretty much right in the middle. Not the best at anything, not the worst at anything, making them seem like a good middleground between DPS and DPH until you see the Dispair ties for best DPS, but doesn't have "worst" anything, making it basically a direct upgrade from the kunai. So Kunai are only good if you can't get Dispair, and want a balance between DPS and DPH This also shows why I didn't include the Mk1 Kinai, they would've been the undeniable worst weapon.
Dispar and Spira both tie for greatest DPH. In my opinion, dispair wins out between these two because of it's higher AS, which gives it the second highest DPS after HikouP, but if, for some reason, you want the extra impact and slash damages, Despair is better than Spira
One would expect the Hikou and Hikou Prime to be a fairly simple comparison, but the generic Hikou actually have more slash damage and attack speed than the HikouP. That being said, it still isn't enough to prevent the HikouP from outmatching the generic Hikou, as the HikouP are better in every other way.
This leaves us with the Hikou Prime, and Dispair. Basically, Dispair has higher DPH, and hikouP has higher DPS. The DPS difference is only 4.1 unmodded, which really doesn't seem like much at first, but keep in mind this gapwill be much larger after modding (in my builds it ends up around 600 DPS).
Also, I realize that the two "best" weapons i've narrowedit down to are the hardest to get, so chanches are someone will want to use the other three as they are much easier to aquire. With that being the case, my suggestion would be Spira for DPH, Hikou for DPS, and Kunai for DPS/DPH balance.
I didn't factor Crit chance/damage into my calculations. The Spira is arguably viable for a crit build (with a maxed pistol gambit it reaches 55% crit chance and with pistol gambitand creeping bullseye, it gets to 67%) but I personally didn't include this because I don't feel that 55% is good enough, and creeping bullseye lowers it's already very low (for thrown weapons) AS. That being said, it is possable that a crit build would elevate the Spira above all other thrown secondary weapons, it is really up to the individual to decide.