General

lol I don't think the attack speed on terminus is worth it. I don't know how funded you plan to be, but if you're super hardcore max damage funded, it's better to just stick to fafnir and just upgrade your damage with decent speed infusion + Green potion. Buff freezers can be bought with meso so Green potion shouldn't be a problem, but I dunno about speed infusion for bosses like Cvellum unless you're using speed infusion on a glove that you're going to wear the entire time.

I mean... I PRESUME Xenon only has 1 attack speed buff. If they have another one, then you don't even need speed infusion. If they don't, then you need it. You could always get Attack Speed IA too. In any case, it's not that detrimental if you aren't at max attack speed if your DPS blade attack does max damage.

Only terminus desperados and whips have the +1 speed fasrer then fafs/sw weps
jk nvm only wep with higher speed is desperado only. go DA's!

SW Chain Sword is Fast(5), ATK 137, 9 slots total. and Terminus Jaegar is Fast(4), 169 ATK with 10 slots total with hammers. I agree with @silentcy. No matter how you slice it Terminus Jaegar is THE weapon for Xenons. It has higher base ATK and one tier faster than SW. Even if you were to transpose a perfected weapon onto a SW it would pale in comparison to a perfected terminus jaegar.
P.S. The 5th through 8th characters in SW is banned. GG Mr.Basil, GG.

Guide for attack speed: http://www.basilmarket.com/Guides-Attack-Speed-Explained-Wiki-303

I think only terminus has a higher att speed for xenon. Unless you're going to use sw set i dont think sw whip would be better. If you wanted higher attack speed with higher attack but no extra boss dmg terminus is the way to go.