Hello,
It is good to choose degree as you have to do degree after diploma.
If you pursue diploma then it will take 2 years and degree thought lateral entry for 3 years in total 5 years.
If you pursue degree then you will take 3/4 years to complete it.
Non medical doesn't mean engineering only. There are many other fields like law, BSc in science subjects , literature, BBA, BA and many more..
So you decide what you want to do and in which stream you can give your best.  Choose it and give your best.
Hope it helps!