I guess my question then becomes, if pure survivability the only potential thing we're looking at? At 7th level some of the beasties you're fighting are using area effect attacks and 7th level hit points ain't exactly a massive guarantee of survival. In addition, to cast either one of those TWO 4th level spells, you don't have room for much else in your arsenal. Is this this pussyfoot mage rumored to exist in legend but rare in actual game play?
I ask because again, in my experience, Fire Shield, Stone Skin, Fire Wall, Evard's black Tentacles etc... are far more likely to be tkane for use in actual play when you're moving into the old dungeon.
But play varies so I ask again if those two spells are the ones most likely to be actively memorized by a 7th level wizard in ye old typical dungeon.
Spells well before 4th help with survival, again such as: false life, mirror image, blink grease, slow, etc. leaving your 2 big spells for necessary control and other party helping measures (summoning spells start becoming big around this level btw.)
The mage's battlefield control also helps with survival, for ex. fire wall and evard's control the battlefield (not to mention if you cast evard's and the enemy can still get off spells (area control or otherwise) you were probably already in big trouble).
When the mage increases in level his use of the lower level spells skyrockets (again from scrolls, wands etc.): at the mid levels this is a bit of a big deal and has no downside (at 7th level a false life and mirror image combo will give the mage more staying power than a rogue while still leaving plenty of room for battlefield control and other offense - the gap only increases from there).
The last time I played a wizard - it just seemed my character was the clear biggest facter at locking down combats and turning supposed difficult encounters into mop-up sessions (we played from 5th-12th level and it was consistant though really amped up around 9-10th, and I wasn't even playing a pure wizard I was playing a fighter/mage though by 9th I was going much more mage than fighter). And in addition to that I was ridiculously useful out of combat too, what with divination spells, knock spells, movement spells(leading to teleportation) etc.
Though to further answer your question - no pure survivability is not the best measure, effectiveness is. And for effectiveness both in and out of combat you're going to find it hard to compete with a mid to high level 3e/3.5e mage.
btw - I suppose I didn't really define effectiveness but to me it's one of those know it when I see it measures.