Go to a degree program bcz in diploma visa success chances are less .........wish u best of luck
I do not think if Diploma courses hold less chance for visa approval. There are number of different courses which can be studied "only by way of Diploma education".
You might have noticed too many Visa rejection in Diploma courses because its "very easy" to get admission (unlike Degree course where there are many stringent requirements before you get into) and as a result lots of undeserving candidature gets rejected.
Keep in mind those who deserve Visa get the same even for a Certificate Course. It doesn't mean Diploma course is less attractive in terms of visa approval.