Yeah thought so...I got it wrong because like a lot of you i chose varchar

Its variable length data so and will need trimming before it can be used if you use char. The question "which is more efficient..." extends beyond the size of the type. without a bit more background on usage i find the question ambiguous

If you said to me a billion rows worked with one at a time, no question, storage is an issue and single rows won't take much trimming so char would be best. But if you said 10,000 rows used widely in joins for many operations then storage is less of an issue and repeatedly trimming spaces is more of an issue.