Singlife accout or CIMB fastsaver

I recently signed up with the Singlife account. You can read about it from other blogger's reviews or from the actual site itself, but to me, it's essentially a savings account. Since I also have CIMB fast saver, I want to explore the decision tree to decide when to put extra funds into CIMB fastsaver or into Singlife account. In my analysis, I'm really going to ignore all the extras, like retrenchment benefits, insurance parts etc of the Singlife account. 

Here's the facts:

Singlife account:

First 10k - 2.5% pa

Next 90k - 1.0% pa

Thereafter - 0% pa

CIMB fast saver:

First 50k - 1.0% pa

Next 25k - 1.5% pa

Next 25k - 1.8% pa

Thereafter - 0.6% pa

Here's the calculations of the interest earned and interest % pa for both:

Singlife account:

CIMB fast saver:

I just did up the interest for the various banding. Straight away we can see that the interest we can get for CIMB is much more for greater amounts of principal put inside, but for smaller amount of principal, Singlife will be more worth it. There must be a point where if I put x amount in Singlife account and the same x amount in CIMB fastsave, the two interest will be the same. And I know x must be somewhere between 75k to 100k.

So, let x be an amount between 75k to 100k,

Amt of interest from Singlife acct: 10,000*0.025 + (x-10,000)*0.01 = 150 + 0.01x 

Amt of interest from CIMB fastsaver: 50,000*0.01 + 25,000*0.015 + (x-75,000)*0.018 = 0.018x - 475

Equating them:

150 + 0.01x = 0.018x - 475

So, x = $78,125

And thus my decision is clear:

To get the highest interest for the same amount of dollars:

I should put it in Singlife account if I have lesser than $78,125

I should put it in CIMB fast saver if I have more than $78,125

If I have exactly $78,125, then I should put it in Singlife account because of the little bit of insurance that I didn't take into account. Both have deposit insurance of up to $75k, so there should be some safety features built into this. 

Okay, now my decision flow is clearer.

Update: 

How silly of me. In the pursuit of deciding either THIS or THAT is better, I forgot that the better solution is a blend of BOTH. Non-duality! Thanks to 15 hww and WGM for pointing this out to me. In light of that, the best solution is put money in both accounts, as shown:

First 10k - put in Singlife account for 2.5% pa - total interest: $250

Thereafter - put in CIMB fastsaver, preferably not more than 100k inside

Done!