If I'm clear, you are doing some or all equalization by transferring RRSP.
The 27.6% is a standard amount that the bank withholds when an RRSP is cashed in. Neither of you is cashing in at this time - if I understand you correctly - but the tax rate is considered so that the actual value of the funds transferred may be determined.
These are not based on your actual tax rate, it is set rate that the bank applies based on the size of the RRSP being cashed in. If you are cashing in a small amount they withhold around 22%, if it is the larger amount, they withhold 27%
Since you may or may not cash in the RRSP immediately, there is no way to absolutely determine the after tax value of the amount, so this tax withholding is what is used. Just to be clear, it is the same as the tax that is withheld from your paycheque and is noted on your T4. If your income is low and your marginal tax rate is much lower, then you would get a refund. The actual tax you pay depends on your income that year, and will change from year to year.
So now let's answer your question. Say he is to transfer $100,000 to you in equalization and is doing it through a spousal RRSP transfer. He would have to transfer $127,600 in RRSP funds to make up for the tax owed. In other words, $127,600 in RRSP is only considered to be $100,000 in cash value.
If he is to transfer $1000 in equalization, then he would transfer around $1220 (I forget the exact percentage.)
If your actual marginal tax rate is lower than 27.6%, and you intend to cash in the funds right away, then the higher rate is to your advantage, because he is transferring a larger sum.
If you are the one making the transfer, then of course the high rate is to his advantage. But keep in mind that this is a standard method of calculation, as far as has been explained to me by my lawyer; it is what a judge would use in the courtroom.