Random Banking Question..

I have Citibank UK and Citibank US accounts.

I want to transfer some money (nothing big) from my UK to US account.

I can just find out by going to an ATM, but where will I have the better rate - taking cash out of my Citibank UK account from an ATM (US) or electronically sending the money from my UK to US account?

The exchange rate if I do it online is US$ 1 to UK£ 0.5152796

Random question, but I figure maybe one of you may know.

At any given time, it ought to be the same, or virtually the same.  I wouldn't sweat that.  Do whatever is more convenient.