Definitely go for Soulshredder. Not only you get one extra sword fighting (compared to what falcon sword gives you). You will also get extra critical damage and most importantly, you will have third imbue slots (for your life leech) and you will feel like a god.
+ if you have low blow unlocked (meaning you have 18% of crit chance instead of 10%) this scales even more with the extra crit damage.
My standard approach would be - if I can get one extra sword fighting for 30kk in training swords, why would I waste 80kk for an item that gives me one extra sword fighting.
Howering in this case we talk about extra critical, extra imbue slot and that is worth it