From what I tested, getting Ilsa/Six the added hits is not worth the raw reduction if you have to choose between two, it would be great to have both which I haven't tested that much atm. What I can say though is that Stamina Opus has been performing great.
Thoughts on Eresh 250: It just got better and fixed a lot of things for 1 turn stuff for me. The removal of skill cap demerit instantly added a lot of damage and the MA boost is also substantial in reaching 100% TA more easily for Cidala and Sariel.
For now I find the S4 underwhelming, this requires purely 76 TA from grid because need added hit to appear on your skill tab for this to work. Ilsa and Six not being hit without some tweaks in grid annoys me.