Does it matter what form savings come in?

Americans save a relatively small percentage of their disposable incomes.  Yet many commentators argue that capital gains on homes and equities, as well as expenditures on education, should count toward the national savings rate.  But are those savings "as good" — from a macroeconomic point of view — as plain old abstinence?  If they were, that would make our lives so much easier; we could worry less about a national shortfall in savings.

To make it interesting assume that the capital gains are not the result of a bubble.  Bubbly asset prices would be an illusory form of savings in the longer run.

Now capital gains in the form of real assets or human capital are less liquid. You might make better widgets, but can lug the machine down to the store to buy groceries?  Will it finance your retirement?  Well, why not?  The advance of capitalism liquifies real assets to an increasing degree; borrow against the assets when you wish.  The still underrated Benjamin Anderson stressed this point in his 1920 The Value of Money. 

So what is the problem?  Does liquifying real assets somehow bring excess leverage to the economy?  I don’t see why.  Or does borrowing against real assets lead to a later switch toward consumption, thereby necessitating transformation costs?  Each individual thinks he has a more liquid savings position than is the case; borrowing is cheap but society as a whole must incur reallocation costs to convert the real capital into consumption.  But how big a factor can this be?

All seems fine.  Yet in my neo-Austrian gut I cannot bring myself to think as capital gains as analytically equivalent to abstinence out of income.

I file this one under the category of "macroeconomic problems I’ve been thinking about for twenty years but haven’t made much progress on."  I’m not even sure I understand what others believe, much less what is true.  I’ve turned on the comments, in case you have a good argument why one form of savings is worth less than another.