According to some white papers on the FICO website, they work very hard to make the distributions come out the same for all three CRAs, so the same overall percentage of people will fall in each bracket. None of them is globally more or less strict. However, each has its own -- secret -- weighting of factors, so any individual will likely have different scores.
Consider an academic analogy: suppose three professors all teach sections of the same course, and agree to grade on a curve such that everybody's AVERAGE will be the same. But each of them has different preferences, different quirks when grading papers (I've graded plenty of undergraduate prose once upon a time, and trust me on this, no matter how fair one tries to be there is an inherent subjective aspect to grading).
In the case of the CRAs, my Experian FICO was 821 last time I pulled it, and the explanation says "no negative factors." My TransUnion was 796, and the explanation mentioned the total balance on my revolving accounts. My Equifax was 787 and the explanation mentioned both the total balance on my revolving accounts and the number of accounts showing a balance.
My wife and I both make good money, have adequate savings, carry very little cash, have long histories with no baddies, and always pay in full at the end of the month. So we run a fair amount of money through our cards, and sometimes have fairly substantial balances at the end of the month on all our cards. Our limits are high enough that our percentage utilization is still quite low. If we wanted we could stop using our credit cards tomorrow and just use debit cards for everything, we've got enough in the bank to do that. We prefer using credit cards for several reasons, however. First, there are some legal protections in the US that only apply to purchases made with a credit card. Second, we get some cash flow benefits from the interest-free grace period of credit cards (I can schedule CC payments for just after paydays and thereby leave more of my money in the Savings Account earning interest). Third, by keeping multiple credit cards active we have access to high credit lines in case of an emergency. Fourth, by using credit cards responsibly we have good FICO scores.
Combining my picture with other postings I've seen, I interpret all this as meaning that for a very clean history, EX cares most about percentage utilization, TU cares more than EX about total dollar amount owed, and EQ also cares more about number of accounts showing a balance on reporting day. So for me the EX score is the highest. But somebody else who has much smaller credit limits but the same balances as my wife and I have on our cards would have a much higher percent utilization and therefore get dinged severely for that on his or her EX FICO score.
Finally, for what little it's worth my Experian "Plus" FAKO score is 812, a little LOWER than my Experian FICO score. Go figure.
TU 791 02/11/2013, EQ 800 1/29/2011 , EX Plus FAKO 812, EX Vantage Score 955 3/19/2010 wife's EQ 9/23/2009 803
EX always was my highest when we could pull all three
Always remember: big print giveth, small print taketh away
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