Once you move beyond net income on Page 3 of the tax return, all that can be transferred between spouses lies on Schedule 1 (and by extension its provincial cousin). Along with the medical expenses, donations, transit passes, and political contributions, Schedule 1 is littered with claims for dependants which could be up for grabs by either spouse. Except for medical expenses, all these claims are not affected by net income, and so all provide the same tax savings to either spouse. Therefore it usually matters little who claims these non-refundable credits, provided they can entirely be applied against both federal and provincial taxes payable.
Medical expenses are special because they are reduced by 3% of net income and can be swapped between spouses. Usually the spouse with the lower net income can make better use of the medical expenses, but this may not be true in cases where only one spouse is eligible to claim the refundable medical supplement, or where the medical expenses are so large that one spouse runs out of tax to apply them against.
Before net income there's only three deductions that can go on either spouse's tax return: Lines 221-carrying charges, 219-moving expenses and 210-elected split pension. These swappable deductions can lower social benefits repaid at Line 235 and net income at Line 236. (Remember that you can also change net income by carrying over some of your RRSP contributions or the business CCA claimed — these are optional deductions.)
A lower net income in turn means a larger old age deduction at Line 301, a larger claim for medical expenses (along possibly with the refundable medical supplement), and it may change who gets to claim the childcare expenses. And if your spouse is claiming you as a dependant at Line 303 (the basis upon which dividends can be transferred between spouses), or claiming amounts transferred at Line 326, then a lower net income for you will increase those claims.
If net income is going down, it's all good news. But a lower net income for one spouse means a higher net for the other, and all the good things go into reverse. My experience is that the poorer you are the more complicated it gets, and everyone is an exception to the rule. The only sure way of getting the best refund is by cutting and pasting between spouses and seeing how tax payable changes.
That is unless there's pension splitting to be done.
Years ago before the split-pension deduction was invented, you were lucky if you could change net income a few hundred dollars and get back a few extra pennies from your medical expenses. Today medical expenses will still be the main bugaboo, but now you can give away half your pension, radically changing your net income, and so everything affected by net income comes into play.

Here's how I split a pension: The Worksheet must be filled in, and I complete everything on both spouse's returns except I never enter the other spouse's net income. This means I'm not filling in Schedule 2 and not claiming a spousal amount at Line 303. I then go to Pension Splitter and hit AutoFind and if necessary I use Search to find the best transfer. If there are medical expenses I switch them onto the other spouse's return and search again. If the other spouse also has pension income to transfer, I repeat the above procedure with the other spouse doing the transferring. I make up a little chart and whichever way comes up with the lowest taxes payable at Line 435 wins.
I then check to see if the best split comes where one spouse has run out of provincial or federal tax to pay. Only if that is so, I then consider switching the other deductions that can go on either spouse's return, like donations and who claims the kids. It's usually when you're trying to make better use of the medical expenses, but often you want to transfer even more pension but you can't because you're already not paying any tax and deductions are being wasted. The solution is to move a deduction over to the other spouse so nothing is wasted. You then have to search again and then maybe swap another deduction, but once you get both spouses paying both federal and provincial tax then there's nothing more you can do.
When I think I have the best split, I exit T1032 letting the program update the spouse's return. Now is the time to enter spouse's net income on Page 1/Schedule 1 and on Schedule 2. But you can't do that until you've gone to the spouse's return so the program can recalculate the new net income. Finally, if there are foreign tax credits, they must be reset and if Line 232, and therefore net income, changes in the process, then it's back to Pension Splitter and do it all over again.