it would depend on if you were using a USB or eSata connector, esata has a similar speed to an internally connected drive. as for noise it would depend on if the external case has a fan or not. an internal drive won't be very noisy especialy if you reduce any vibration.
so for the questions you asked either would be fine, the next question is what are you going to be using it for? if you want to be able to access the data on other PCs go for an external