In Amex's T&C, it says they won't do a BT> 50% of the credit line you get.
Even if you don't believe that Amex likes pif, they are whacky with how they charge interest, they charge it as often as they can- so don't carry a balance on Amex.
Both of mine are at 0% util currently.
Now Discover, Discover likes balance carrying... Hell they'll cli ya when you have high util.
Marriott PR$25k | BCE $24.5K |BankAmericard Visa $25k| BOA Better Bal $17.5k |Wmt Discover $12.5k | BR Visa $17.5k | Amex Delta Gold $10k | Discover IT $10k | Paypal Extras MC $15k | Amazon Store $10k|Smile Gen $7.25k | Dillard's $10k | West Elm $4k| Express $3.05K | Mypoints.com Visa $4.5k | Freedom Visa $1k| Amex Surpass $1k