forms - Splitting credit card number fields into four different inputs

I have previously been using 4 fields for the credit card number, splitting up each set of 4 numbers to make it easier to enter.

I am now thinking about having one field, which inserts spaces after every set of numbers instead:

For the one with 4 fields, the cursor jumps to the next field automatically.

Which format is preferred? Or are there any other better alternatives?

I only accept Visa, Mastercard and Discovery, with 16 and 17 digits.