Best in slot - general topic

i am standing in the AH and want to buy a better cape for my resto shaman.
I have no problem of seeing that a ilvl 445 cape cloak of blessed detsh is the best.
But it costs like 300k
Now the “same” cloak ilvl 435 is much cheaper.
Now in the drop down box for the slot i an see how much better the ilvl 445 is related to the 435, but I cant see if the 435 ilvl is better then the one (420 not the same stat ofc ) i have already ?
Its odd that the number is not how much better the item in the list box is relatively to the one u already wear (and then the greater number is better ofc)?
I then assumed there would be some mark,icon or color to show the one u already wear, but i cant seem to find it.

I assumed then that when the one ilvl 445 is better then the 435 is also better, but surely that is not the case every time ? example: if the one i have have the leviathans 120 intelligence, its not certain that the cape of lets say 425 is better ?

And yes, i am a healer and 71 yrs old so to ilvl up as healer , i buy it if i can.(afford)