Both have pros and cons
I fully use powdered formula now, but when my son was first born I would use the enfamil liquid formula in his baby bag when I was going places since they were so quick and easy to prepare. But the liquid formulas are so expensive!
Powder isn't much better but luckily I get a bit of help there from the wonderful WIC program.
Now that there are so many powder dispensers that are easy for when you're on the go liquid formula doesn't seem worth the money.