Credit card debt, by far. I just read an article this morning on MSN that quoted Barry from MyFico saying that paying down installment loans has little to no impact to your credit scores. Paying down revolving debt has a very positive impact on your scores --- depending on total balances and available credit of course. 
It would actually help your score more if you pay down my revolving balances
Just kidding!
Credit card would be best to pay off. Always remember, revolving credit holds a big junk of weight on your credit score over any other credit you may have. Just to give you an example: I never needed credit before so just decide to get some, don't know why, just did. So, I went out and financed a car for $20,000.00. I paid the car for 6 months (because that is the time it takes to get fico score) on the 6th month I paid down 97% of the loan just leaving a little balance to sit on my credit a little longer to help me get a good score. So now, my debt to credit ratio is only 3% NOT 100% AS it was when I financed it. So, to continue to help my credit, I went to get a cc. Got one through HSBC (orchard bank) with a $300.00 credit line. I used $268 of the credit so I can show activity on my report. Well, even though I paid 97% of the car loan, my fico came in under 600 all because I used about 89% of my revolving credit! It was as if my car loan and the low balance was never there! Who would have thought that by me useing B.S. $288 on a $300 cc would have more weight then me paying down 97% of a $20,000 car note in just 6 months. Go figure!!
I hope this helps. Always keep cc balances low, if not, I will bite you were the sun does not shine, ouch!! 
TexCredit wrote:I just read an article this morning on MSN that quoted Barry from MyFico saying that paying down installment loans has little to no impact to your credit scores. Paying down revolving debt has a very positive impact on your scores --- depending on total balances and available credit of course.
Link available?