Okay, the stock in the 4-year stock grant is imaginary in the same sense that your future salary is imaginary. I mean, fine, call it imaginary if you want, but that's true of all pay.
The Google vesting schedule, AFAIK, is 1-year cliff and then quarterly vesting thereafter. Which means that, past the first year, at most 90 days of stock is money that might vanish if you leave. I agree it'd be a lot nicer if it vested daily, but it's completely silly to characterize this as imaginary. It would also be completely silly, supposing that you'd worked at Google for 17.9 months and gotten 15 months of stock vestiture, to describe the stock you get 3 days later as a "windfall".
The point of all this is that it is completely reasonable, when discussing how much Google paid a person, to sum up their base pay, plus their bonus, plus the value of the amount of stock that they vest in a year.
If you're choosing between an offer at Google, say with $110k plus 15% bonus target plus 4 years of stock currently valued at $180k (i.e. roughly $45k per annum, probably more by the time it vests), vs working at a startup offering a base pay of $150k (plus say 10% bonus target dependent on revene, and some joke amount of stock valued at some joke number), I think it's pretty obvious that purely from an expected-value-financial-benefit standpoint, you should go with El Goog. Because "total comp" is a real thing. (Not that any sane person thinks that's the most important aspect of such a choice.)